Anyone know of a good demonologist core class?

[Nifft]

IMHO, Poison is a higher-level power because it's both too potent, and not potent enough, at low levels.

1/ Too potent: It's really hard to heal ability damage at low levels.

2/ Not potent enough: Who cares if you lose 8 Con at 1st level? That's -4 hp (in other words, "goblin damage"). At 10th level, that's 40 hp -- quite a few more.

So, it works out to be mostly annoying at low levels, IMHO.

-- N

 

[Erekose]

OK - a bit of a change around but here's a (hopefully) final version of the class.

DIABOLIST
Alignment: Chaotic evil, chaotic neutral, neutral evil.
Hit Die: d8.
Class Skills: The diabolist’s class skills (and the key ability for each skill) are Concentration (Con), Craft (Int), Decipher Script (Int), Intimidate (Cha), Knowledge (all skills, taken individually) (Int), Profession (Wis), and Spellcraft (Int).
Skill Points at 1st Level: (2 + Int modifier) x4.
Skill Points at Each Additional Level: 2 + Int modifier.
BAB/SAVES: As Cleric.
Weapon and Armour Proficiency: A diabolist is proficient with all simple weapons, light armour, medium armour, and shields (except tower shields).

Special Abilities
Level Special
1st Demonic Bond (Gutworm [FF])
2nd Demonsight
3rd Summoning (Mane [BoVD])
4th Resistances 5
5th Summoning (Dretch [MM1])
6th Poisoned Touch 1/day
7th Summoning (Rutterkin [MM1])
8th Demonic Familiar (Quasit [MM1])
9th Summoning (Bar-Igurra [MM1])
10th Poisoned Touch 2/day
11th Summoning (Jovoc [MM2])
12th Ritual, Resistances 10
13th Summoning (Babau [MM1])
14th Poisoned Touch 3/day
15th Summoning (Vrock [MM1])
16th Demonic glare
17th Summoning (Bebilith [MM1])
18th Poisoned Touch 4/day
19th Glare of the Abyss
20th Soulless

Demonic Bond (Su): As part of his or her pact with a demon lord, the diabolist willing consumes whole a gutworm. The gutworm acts as the focus for the diabolist to call upon his or her demonic patron for all subsequent abilities. Should the gutworm die, the diabolist loses all of the special abilities associated with the diabolist class until it is replaced.

{I have the FF on order but haven't had it delivered yet; in another post Gez has listed the salient abilities gained from hosting the abyssal parasite as: "Gives a inherent boost to Constitution, and can incite a barbarian-like rage in the host at will, without causing fatigue in the host. Once per day, they can neutralize ingested poison in their host." This sounds too powerful for 1st level - I'll need to tweak it when I see the full details in the book.}

Demonsight (Su): At 2nd level and higher, a diabolist can see in the dark up to 60 feet. Demonsight is black and white only, but it is otherwise like normal sight.

Summoning (Su): At 3rd level and higher, a diabolist can perform a summoning that takes 1 round to petition his or her demon lord for aid. This comes in the form of a demon, which will fight on behalf of the diabolist for a maximum of 1 round per diabolist level. Summoned demons cannot call other demons to their aid. A diabolist may call more powerful demons as he or she increases in level. A diabolist may only call a particular type of demon, e.g. a bebilith, once per day.

Demonic Resistance (Ex): At 4th level, the diabolist gains resistance to acid/cold/electricity/fire 5. At 12th level, this resistance increases to 10.

Poisoned Touch (Su): As a standard action, a diabolist can calling upon his or her demonic patron to infect an opponent with a horrible poison by making a successful melee touch attack. The poison deals 1d10 points of temporary Constitution damage immediately and another 1d10 points of temporary Constitution damage 1 minute later. Each instance of damage can be negated by a Fortitude save (DC 10 + diabolist level + Charisma modifier). The number of times a diabolist can use this ability increases with level (i.e. 1/day at 6th, 2/day at 10th, 3/day at 14th and 4/day at 18th level).

Demonic Familiar: Improved Familiar (Quasit).

Ritual (Sp): At 12th level and higher, once per day, a diabolist can perform a ritual to petition his or her demon lord directly, for an answer to a particular question. The ceremony takes one hour to perform and the answer is in the form of yes, no, may be, or unknown. The demon lord is not omniscient. It knows all observable facts about the present, and can thus answer questions like, “Is there a guard on the other side of this wall?” but it can only speculate on the future, e.g. “Will I be able to climb Mount Raundan and enter the City of Aras unseen?”.

Demonic Glare (Su): As Fiendish Glare from Acolyte of the Skin.

Glare of the Abyss (Su): As Glare of the Pit from Acolyte of the Skin.

Soulless (Su): At 20th level, a diabolist’s soul is forever damned to the abyss. He or she becomes an outsider (native) with damage reduction 10/good.

 

[yennico]

Sorry, I can not comment your class today because I have too much to do.
I will comment your class tomorrow.

 

[Sigurd]

You might want to abstract the gut worm with some sort of infernal conduit.

Consider removing the Chaotic Neutral option. Its not like a character would be allowed to be anything but evil by infernal masters.

S

 

[yennico]

Here are my comments.
First I like your concept.
Even if you disagree I see your class a cleric with only divine summon monster spells.

DIABOLIST

I dislike this name. Diabolist sounds like diabolic
I also remember a class called diabolist from Palladium Fantasy RPG. This class use power words, runes...

In Palladium Fantasy RPG exists a class called witch. This class made a pact with an evil force and gained either the gift of power (hit points and other special abilities), gift of magic (spells) or the gift of union (the most powerful gift: some abilities from the gift of power and some of the gift of magic).

I know there exists in D&D a class called witch.
I will refer to your class as demonic summoner.

Class Skills: The diabolist’s class skills (and the key ability for each skill) are Concentration (Con), Craft (Int), Decipher Script (Int), Intimidate (Cha), Knowledge (all skills, taken individually) (Int), Profession (Wis), and Spellcraft (Int).

Better to read: Class skills: as wizard + Intimidate.
Perhaps you can add diplomacy to this list.

Skill Points at 1st Level: (2 + Int modifier) x4.
Skill Points at Each Additional Level: 2 + Int modifier.

Your summoner is a divine spellcaster, so his key attribute for spells is Wis.
Also important attributes are St and Con, because the summoner is also a fighter.
You can increase the skill points to 4 + Int (like a cleric)

2nd Demonsight

A race with already darkvision gains nothing?

9th Summoning (Bar-Igurra [MM1])

You have dropped the poison immunity. You can enter this ability here.

Demonic Bond (Su): As part of his or her pact with a demon lord, the diabolist willing consumes whole a gutworm.

A gut worm is a "good" symbiont for a pure fighting class who do not rely on summonings.
If a fighter with a gut worm can not enter an area because of some spells he can fight with ranged weapons.

The gutworm acts as the focus for the diabolist to call upon his or her demonic patron for all subsequent abilities. Should the gutworm die, the diabolist loses all of the special abilities associated with the diabolist class until it is replaced.

This is no good idea. At high level a gut worm easily can be killed and then a demonic summoner looses all his abilities.
How does the summoner replace his gut worm if he has no summon gut worm spell?

{I have the FF on order but haven't had it delivered yet; in another post Gez has listed the salient abilities gained from hosting the abyssal parasite as: "Gives a inherent boost to Constitution, and can incite a barbarian-like rage in the host at will, without causing fatigue in the host. Once per day, they can neutralize ingested poison in their host." This sounds too powerful for 1st level - I'll need to tweak it when I see the full details in the book.}

One of my friends owns the book and I looked up the gut worm.
The gut worm is a fiendish symbiont, so the host creature gains outsider traits: darkvision (60 ft.), becomes an outsider and can communicate by telepathy with the symbiont.
Becoming an outsider at level one is a big disadvantage for a summoner. An outsider summoner can not enter some areas. The same areas his summoned monsters also can not enter.
You can compare a demonic summoner level 2 with gut worm with a tiefling cleric 1.
The gut worm has also a big drawback. A remove disease spell (Cleric 3) kills the gut worm and the host creature takes 4d6 + losing the enhanced con 1hp/level of the demonic summoner damage.
IIRC Fiend Folio was a 3.0 book so a demonic summoner with a gut worm becomes an outsider (native).

Summoning (Su): At 3rd level and higher, a diabolist can perform a summoning that takes 1 round to petition his or her demon lord for aid.

Add this text: The summoning acts in all ways like a divine summon monster spell of the same name.

This comes in the form of a demon,

This is too restrictive. Write: This comes in form of a CE extraplanar creature.
So a demonic summoner also can summon fiendish animals.

Fiendish creatures dwell on the lower planes, the realms of evil,

which will fight on behalf of the diabolist for a maximum of 1 round per diabolist level.

This is also too restrictive. A summoned creature can do more than fighting.
A demon can open a trapped chest, deliver a message as long the duration of the spell lasts, etc...
Reading your description I am reminded of summoning wizards out of a video game.

A diabolist may only call a particular type of demon, e.g. a bebilith, once per day.

No. This is too little. A demonic summoner should be able to summon more than:
One mane, one dretch, one bar-lgurra, one jovoc, one babau, one vrock and one bebilith.
With your restriction a demonic summoner can not use a summon monster III to summon 1d3+1 manes, a summon monster II monster.

Ritual (Sp): At 12th level and higher, once per day, a diabolist can perform a ritual to petition his or her demon lord directly, for an answer to a particular question. The ceremony takes one hour to perform and the answer is in the form of yes, no, may be, or unknown. The demon lord is not omniscient. It knows all observable facts about the present, and can thus answer questions like, “Is there a guard on the other side of this wall?” but it can only speculate on the future, e.g. “Will I be able to climb Mount Raundan and enter the City of Aras unseen?”.

This ritual is exactly like the cleric´s commune spell. There are only two differences.
1. the duration: A cleric needs only 1round/level
2. the number of questions: A cleric can ask 1 question/per level

 

[yennico]

Here are my suggestions.
IMHO your class is underpowered. Your version of the summoner has to many weaknesses and restrictions. I think a video game high level summoner will not survive a dungeon.

There is a big diference between your class and a CE cleric specialized in summoning.
The cleric has also other useful spells. Not only the buff spells also spells e.g. dispel magic to negate protection from evil spells.

I think your class could also work for a LE summoner who summons devils and a NE summoner who summons yugoloths.

I try to rebuild your class. If you dislike my proposal ignore it.

Demonic summoner aka daemonologist aka soulless cleric

Alignment: Chaotic evil, chaotic neutral, neutral evil.
Hit Die: d8.

Perhaps I should drop the chaotic neutral alignment like Sigurd suggested.

Class skills: as wizard + Intimidate + Diplomacy.
Skill Points at 1st Level: (4 + Int modifier) x4.
Skill Points at Each Additional Level: 4 + Int modifier.

BAB/SAVES: As Cleric.
Weapon and Armour Proficiency: A diabolist is proficient with all simple weapons, light armour, medium armour, and shields (except tower shields).

Spells: a demonic summoner casts divine spells. He can cast spells only from a special spell list.
Spells per day: same as druid except a demonic summoner gets no 0-level spells.


Special Abilities
Level Special
1st Patron: Demon, Darkvision, Smite Good 1/day
2nd
3rd
4th SR, Resistances 5
5th
6th
7th
8th Demonic Familiar (Quasit [MM1])
9th Venom Immunity
10th
11th
12th Resistances 10
13th
14th
15th
16th Demonic glare
17th
18th
19th Glare of the Abyss
20th Soulless

Patron Demon: The demonic summoner chooses a demon as his patron. This demon acts like a god for a cleric. The demon grants the demonic summoner the spells and the special abilities. If the demonic summoner looses his faith in the demon the demon do not grant the demonic summoner any spells and revokes the special abilities of the demonic summoner.

SR: Spell resistance equal to creature’s HD + 10 (maximum 35)

Resistance (Ex): At 4th level, the demonic summoner gains resistance to acid/cold/electricity/fire 5. At 12th level, this resistance increases to 10.

Venom Immunity (Ex): At 9th level, a druid gains immunity to all poisons.

Demonic Familiar: Improved Familiar (Quasit).

Demonic Glare (Su): As Fiendish Glare from Acolyte of the Skin.

Glare of the Abyss (Su): As Glare of the Pit from Acolyte of the Skin.

Soulless (Su): At 20th level, a diabolist’s soul is forever damned to the abyss. He or she becomes an outsider (native) with damage reduction 10/good.

Spell list:
In addition to the spells Summon Monster I-IX (CE outsider only)
Level 1: Protection from good/law
Level 2: Darkness, desecrate
Level 3: Contagion, dispel magic, magic circle agianst good/law
Level 4: Dismissal, lesser planar ally, poison, unholy blight
Level 5: Commune, dispel good, unhallow
Level 6: Banishment, forbiddance, greater dispel magic, planar ally
Level 7: Blasphemy, destruction
Level 8: greater planar ally, unholy aura
Level 9: Gate, miracle

Design Note: I have choosen the spells a half-fiend recieves (except horrid wilting) plus your ritual and some other useful spells.

 

[yennico]

Erekose: Have you read my last posts? Do you stop building the demonologist class?

 

[Erekose]

Erekose: Have you read my last posts? Do you stop building the demonologist class?

Sorry yennico! Work and well . . . just life in general have kept me away from ENWORLD

I do appreciate your help with this!

I can see why you have suggested the changes in the class but to be honest this takes it into exactly the direction that I do not want it to go, i.e. a variant cleric.

My idea was for an ordinary person who would otherwise had an NPC class like Expert but has become so desperate and disillusioned that he or she has petitioned a demon lord. The person has no actual magical power of their own but is rather just a conduit for the demon lord into the mortal realm.

I know this could be considered similar to the cleric but in my mind it is fundamentally different.


Where I have current got to with the class is as follows:

DIABOLIST (until I can think of a better name!)

Alignment: Chaotic neutral, chaotic evil or neutral evil.
Hit Die: d8.
BAB/SAVES: As Cleric.
Class Skills
The diabolist’s class skills (and the key ability for each skill) are Concentration (Con), Craft (Int), Decipher Script (Int), Intimidate (Cha), Knowledge (all skills, taken individually) (Int), Profession (Wis), and Spellcraft (Int).
Skill Points at 1st Level: (4 + Int modifier) x 4.
Skill Points at Each Additional Level: 4 + Int modifier.

Class Features

All of the following are class features of the diabolist.

Weapon and Armour Proficiency: A diabolist is proficient with all simple weapons, light armour, medium armour and shields (except tower shields).

-- Special
1 - Bonus language, demonic bond (wrath)
2 - Demonic bond (neutralise poison), demonsight
3 - Call demon (mane), demonic bond (vitality)
4 - Demonic resistance 5, superior calling +1
5 - Call demon (dretch)
6 - Poisoned touch 1/day
7 - Call demon (rutterkin)
8 - Demonic familiar (quasit), superior calling +2
9 - Call demon (bar-igurra)
10 - Poisoned touch 2/day
11 - Call demon (jovoc)
12 - Demonic resistance 10, superior calling +3
13 - Call demon (babau), ritual
14 - Poisoned touch 3/day
15 - Call demon (vrock)
16 - Demonic glare, superior calling +4
17 - Call demon (bebilith)
18 - Poisoned touch 4/day
19 - Glare of the abyss
20 - Soulless

Bonus Language: The diabolist learns the language of demonkind, Abyssal, as a bonus language.

Demonic Bond (Su): As part of his or her pact with a demon lord, the diabolist willing becomes infected with a gutworm. The gutworm acts as the focus for the diabolist to call upon his or her demonic patron for all subsequent abilities. Unlike the standard parasite-host relationship the gutworm normally establishes with its host, the gutworm becomes a normal part of the diabolist and so is not affected by spells such as cure disease.

Wrath (Ex): At 1st level, the diabolist can take advantage of the gutworm’s ability to incite a frenzy in it’s host once per day. The diabolist gains +4 Strength, +4 Constitution, and a +2 bonus on Will saves but suffers a -2 AC penalty. The frenzy lasts for only 4 rounds but the diabolist is not fatigued afterwards.

Neutralise Poison (Su): From 2nd level, the level of integration of the gutworm with the diabolist deepens. Once per day, the gutworm will automatically neutralise the first poison that is introduced into the diabolist’s body.

Vitality (Ex): The integration of the gutwrom into the diabolist’s body is completed at 3rd level. The gutworm enhances the diabolist vitality with a +2 inherent bonus to his Constitution score.

Demonsight (Su): At 2nd level and higher, a diabolist can see in the dark up to 60 feet. Demonsight is black and white only, but it is otherwise like normal sight.

Call Demon (Su): At 3rd level and higher, a diabolist can perform a calling that takes 1 round to petition his or her demon lord for aid. This comes in the form of a demon, which will fight on behalf of the diabolist for a maximum of 1 round per diabolist level. Called demons cannot summon other demons to their aid. A diabolist may call more powerful demons as he or she increases in level. A diabolist may only call a particular type of demon, e.g. a bebilith, once per day.

If the diabolist does not dismiss the demon before the duration of effect ends, the summoned demon remains in the mortal realm and is no longer subject to the diabolist’s command.

Demonic Resistance (Ex): At 4th level, the diabolist gains resistance to acid/cold/electricity/fire 5. At 12th level, this resistance increases to 10.

Superior Calling (Su): From 4th level and higher, the demons that answer a diabolist’s call are more powerful than normal. Each demon has +1 hit dice per 4 levels a diabolist has up to a maximum of +4 (i.e. +1 at 4th, +2 at 8th, +3 at 12th, and +4 at 16th level).

Poisoned Touch (Su): As a standard action, a diabolist can call upon his or her demonic patron to infect an opponent with a horrible poison by making a successful melee touch attack. At 6th level, the poison deals 1d10 points of temporary Constitution damage immediately and another 1d10 points of temporary Constitution damage 1 minute later. Each instance of damage can be negated by a Fortitude save (DC 10 + diabolist level + Charisma modifier). The number of times a diabolist can use this ability increases with level (i.e. 1/day at 6th, 2/day at 10th, 3/day at 14th and 4/day at 18th level).

Demonic Familiar: From 8th level onwards, a diabolist can request his or her demon lord for a quasit as a demonic familiar.

Ritual (Sp): At 12th level and higher, once per day, a diabolist can perform a ritual to petition his or her demon lord directly, for an answer to a particular question. The ceremony takes one hour to perform and the answer is in the form of yes, no, may be, or unknown. The demon lord is not omniscient. It knows all observable facts about the present, and can thus answer questions like, “Is there a guard on the other side of this wall?” but it can only speculate on the future, e.g. “Will I be able to climb Mount Raundan and enter the City of Aras unseen?”.

Demonic Glare (Su): As Fiendish Glare from Acolyte of the Skin.

Glare of the Abyss (Su): As Glare of the Pit from Acolyte of the Skin.

Soulless (Su): At 20th level, a diabolist’s damned soul becomes demonic. He or she becomes an outsider (native) with damage reduction 10/good.

 

[yennico]

I can see why you have suggested the changes in the class but to be honest this takes it into exactly the direction that I do not want it to go, i.e. a variant cleric.

I do not say your class is a cleric or a cleric variant.
I compared your class with a cleric because of three reasons:
1.) the cleric seemed to the most fitting class to be compared with your class
2.) your class get his powers form an outsider (a demon) which is similar to a cleric and his deity
3.) the abilities of your class are magical. They must be either divine magic, because your class can wear armor and use this abilities or these abilities must be spell-like abilities.

My idea was for an ordinary person who would otherwise had an NPC class like Expert but has become so desperate and disillusioned that he or she has petitioned a demon lord.

?? This sounds like a prc to me. It sounds that you want to build an prestige class rather than a core class.
Your class is a core class. Every character class level 0 or any character with a nyclass can enter your class. You can build a prc out of your class which every class can enter.

I assume that every character level 6 can enter your diabolist prc.
It is not so easy to make a prc which is available for commoners and!!! other classes at level 6, because the commoner has the lowest saves, BAB, etc. If you use BAB, Saves as requirements other classes can achieve the requirements before advancing to level 6.

Requirements:
Alignment: Chaotic neutral, chaotic evil or neutral evil.
Skills: two skills at rank 9
HD: 6 HDs
Feat: Demonic Thrall
Attributes: int at least 8

I choose the requirements because some monsters can have 9 ranks in two skills and also have 6 Hds.

Perhaps you may add further requirements:
Demons favour strong personalities: Cha 13+
Demons favour only physical strong persons: Str 13+
Demons favour only persons with strong personalities and physical strength: Cha 13+ and Str 13+

A prc can be more powerful than a core class. If a character can enter the prc at level 5 instead of 6 you can give the prc access to summon monster IV at level 7 (2nd level of the prc)

Hit Die: d8.
BAB/SAVES: As Cleric.
Class Skills
The diabolist’s class skills (and the key ability for each skill) are Concentration (Con), Craft (Int), Decipher Script (Int), Intimidate (Cha), Knowledge (Arcana, Planesy) (Int), Profession (Wis), and Spellcraft (Int).
Skill Points at 1st Level: (4 + Int modifier) x 4.
Skill Points at Each Additional Level: 4 + Int modifier.

Class Features

All of the following are class features of the diabolist.

Weapon and Armour Proficiency: A diabolist is proficient with all simple weapons, light armour, medium armour and shields (except tower shields).

-- Special
1 - Demonic Bond (wrath and neutralize poison), bonus language
2 - Demonsight, Call Demon (Summon Monster IV)
3 - Demonic Bond (Vitality) Outsider (native)
4 - Demonic resistances 5, Call Demon (Summon Monster V)
5 - Demonic familiar (quasit), Poison 3x/day
6 - Call Demon (Summon Monster VI)
7 - Demonic Glare, Natural Armor +2 (or another ability)
8 - Glare of the Abyss, Call Demon (Summon Monster VII)
9 - Demonic resistance 10, ritual
10 - Soulless: DR 10/good Call Demon (Summon Monster VIII)

Call demon is a spell like ability (CL= HD) which can not be enhanced by augment summoning or any metamagic feat. It can only enhanced by feats which enhanced spell-like abilities.

I know this could be considered similar to the cleric but in my mind it is fundamentally different.

This sounds like a mutation based on the ingested gutworm on me. Your class get its power from the demon blood in his body similar to a sorcerer.

(Int), Decipher Script (Int), Intimidate (Cha), Knowledge (all skills, taken individually) (Int), Profession (Wis), and Spellcraft (Int).

You want to build a class or prc for a NPC expert who is disilllusioned and petitioned a demon.
With all knowledge skills as class skills the expert becomes a sage. I would limit the knowledge skills to: Planes, Arcana and perhaps religion.

Demonic Bond (Su): As part of his or her pact with a demon lord, the diabolist willing becomes infected with a gutworm. The gutworm acts as the focus for the diabolist to call upon his or her demonic patron for all subsequent abilities. Unlike the standard parasite-host relationship the gutworm normally establishes with its host, the gutworm becomes a normal part of the diabolist and so is not affected by spells such as cure disease.

I really love the idea how you revised demonic bond. IMC I would make only one small change: The demon gives the knowledge how to perfom a special ritual on a gutworm. In this ritual which oly a person with a demonic thrall feat can perfom the diabolist ingests only blood of a gut worm. This blood is the focus for the diabolist to call upon his powers.
The diabolist can teach the ritual only to everybody with the demonic thrall feat. Any person who tries to raid this secret ritual out of the mind of a diabolist either by spell, diplomacy or otrher means gets a curse on himself. Nobody without the demonic thrall feat understands what the diabolist says if he speaks about the ritual.

Wrath (Ex): At 1st level, the diabolist can take advantage of the gutworm’s ability to incite a frenzy in it’s host once per day. The diabolist gains +4 Strength, +4 Constitution, and a +2 bonus on Will saves but suffers a -2 AC penalty. The frenzy lasts for only 4 rounds but the diabolist is not fatigued afterwards.

the special treated blood of the gutworm grants this power to the diabolist... The wrath is like the barbarian rage ability except that the duration is limited to four rounds and the diabolist is not fatigued afterwards and this ability do not stack with any rage ability.

Neutralise Poison (Su): From 2nd level, the level of integration of the gutworm with the diabolist deepens. Once per day, the gutworm will automatically neutralise the first poison that is introduced into the diabolist’s body.

Sounds ok because it is limited to the body of the diabolist.

If the diabolist does not dismiss the demon before the duration of effect ends, the summoned demon remains in the mortal realm and is no longer subject to the diabolist’s command.

Very nice feature.
Does a dismissal or banishment send these demon back to their home plane?
Does a demon who is no longer under the command of a diabolist attack the diabolist?
Call Demon sounds like a planar ally with payment: after finishing the service stay on the material plane to me

Superior Calling (Su): From 4th level and higher, the demons that answer a diabolist’s call are more powerful than normal. Each demon has +1 hit dice per 4 levels a diabolist has up to a maximum of +4 (i.e. +1 at 4th, +2 at 8th, +3 at 12th, and +4 at 16th level).

+1 hit dice means for an outsider: +1d8, +1 BAB, +1 on each save and 8+ int mod skill points. I do not know how I should rate this ability. +1 hd +1 bab +1 saves sounds like +1 CR for this demon, at level 16 +4 CR.
Can this ability combined with augment summoning?

Soulless (Su): At 20th level, a diabolist’s damned soul becomes demonic. He or she becomes an outsider (native) with damage reduction 10/good.

IMHO you can give the type outsider (native) only after the complete transformation of the gut worm, so the diabolist is immune to charm person.

I really like this version. I have only one problem.
I can see this class as elite member of a cult who worships demons, but I can not see this class as class for a disillusioned NPC expert.
A NPC expert e.g. a shoemaker who petitioned a demonic lord becomes a diabolist.
He gets a benefit: Demonic Bond, but he has to change his life because of the skill list he also has to become a sage.
After reaching level 5 the NPC expert gets no real benefit.
How often does a NPC expert need to summon demons which fight for him if he stays in a city. The call demon ability is for adventuring persons, so if the NPC expert/diabolist wants to use this ability often he has to abandon his former lifestyle. Also the poisonous touch ability is for persons who fight often.

 

[yennico]

One option for a replacement of your superior calling can be this:
A diabolist can summon only one specific fiend of which he knows the true name.
Each specific fiend can be summoned only once per day. A diabolist can summon each fiend more than once but every summoning beyond the first costs the number of summonings of permanent hps e.g. to summon a fiend twice per day costs two permanent lost hps.
Each fiend which survives an encounter can be send back to his native plane by the summoner if the fiend failes a will save versus DC 10 + level of the diabolist prc.
If the fiend returns to his native plane he receives XPs for the combat. After surviving several fights a fiend can advance a hit die.
The call demon ability is like a planar ally. If a fiend dies in a fight on the material plane the fiend receives no XPs and he is dead. So the diabolist must be cautious if he calls a demon for his help. After the death of one of his fiends the diabolist must learn a new true name of a fiend of that type. The new fiend has 0 Xps. Learning a new true name is painful and costs the diabolist 1 permanent hp.