So here's my take on the Aboleth Savant, which I'm estimating to be CR 13. There are actually four "versions" of Aboleth Savants with different spell lists, so there may be some variation in CR. The version below has a spell list geared toward conjuration. I may look for further ways to distinguish the four "versions" (Conjurer, Enchanter, Transmuter, and Illusionist - which was a Necromancer in the original
Night Below but didn't make sense).
To begin, here's how I reverse calculated the MM Aboleth's CR. According to my numbers it looks more of a CR 9 than 10, but like with a lot of things in 5e, the proof is in the play and it's not worth splitting hairs over.
[SBLOCK]
Aboleth (CR 9)
final CR 9 = (8 + 10) / 2
defense CR 8 = 6 (hp 135 +20 =155) + 2 (ac 17 +2 saves)
offense CR 10 = 9 (DPR 60) + 1 (attack +9)
DPR 60 = (39 + 61 + 81) / 3
(1st round) enslave + psychic drain + tail + charm victim’s attack (~2d8+5) = 0 + 10 +15 + 14 = 39
(2nd round) multiattack + psychic drain + tail = 36 + 10 + 15 = 61
(3rd round) multiattack + tailx3 = 36 + 45 = 81[/SBLOCK]
And here's how I calculated the Aboleth Savant's CR 13. You'll notice that I didn't have it use its Enslave ability. In my campaign, by the time the PCs reach the Aboleth Savants they'll likely have completed a ritual granting themselves and their companions immunity to aboleth domination, so in this case the Aboleth Savant's psychic drain is being used on a pre-existing enslaved minion, not a PC.
[SBLOCK]
Aboleth Savant, conjurer (CR 13)
final CR 13 = (10 + 16) / 2
defense CR 10 = 9 (hp 170 + 28 =198) + 1 (ac 17 +2 saves)
offense CR 16 = 17 (DPR 110) -1 (attack +9, spell save DC 17)
DPR 110 = (104 + 104 + 123) / 3
(1st round) vitriolic sphere (hits 2 in 20-ft radius) + psychic drain + tail = 75 + 14 + 15 = 104
(2nd round) vitriolic sphere (hits 2 in 20-ft radius) + psychic drain + tail = 75 + 14 + 15 = 104
(3rd round) multiattack + tailx3 + wounded fury (x6) = 36 + 45 + 42 = 123[/SBLOCK]
Upgrades the Aboleth Savant receives over the MM Aboleth:
- Size increased to Huge, HD to 20d12 + 40
- +1 Intelligence
- Spellcasting, 11th level, from any spell list
- Wounded Fury, from the Quaggoth in MM
- Enslave improved with greater frequency, improved range, and harder DC
- Psychic Drain legendary action 4d6 instead of 3d6
Sources:
Night Below by Carl Sargent, 1995
Ecology of the Aboleth by Brandon Grist, DRAGON 131, 1988
Aboleth Savant, The Conjurer
Huge aberration, lawful evil
Armor Class 17 (natural armor)
Hit Points 170 (20d12 + 40)
Speed 10ft., swim 40ft.
STR 21 (+5)
DEX 9 (- 1)
CON 15 (+2)
INT 20 (+5)
WIS 16 (+3)
CHA 18 (+4)
Saving Throws Con +6, Int +8, Wis +7
Skills Arcana +13, History +13, Perception +11
Senses darkvision 120 ft., tremorsense 120 ft., passive Perception 21
Languages Deep Speech, telepathy 120ft.
Challenge 13 (10,000 XP)
Amphibious. The aboleth savant can breathe air and water.
Mucous Cloud. While underwater, the aboleth savant is surrounded by transformative mucus. A creature that touches the aboleth savant or that hits it with a melee attack while within 5 feet of it must make a DC 15 Constitution saving throw. On a failure, the creature is diseased for 1d4 hours. The diseased creature can breathe only underwater.
Probing Telepathy. If a creature communicates telepathically with the aboleth savant, the aboleth learns the creature's greatest desires if the aboleth can see the creature.
Spellcasting (conjuration). The aboleth savant is an 11th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 17, +9 to hit with spell attacks). It has the following spells prepared, requiring no material components:
Cantrips (at-will):
acid splash, eldritch blast, mage hand, minor illusion
1st level (4 slots):
arms of hadar, detect magic, fog cloud, witch bolt
2nd level (3 slots):
darkness, misty step, shatter
3rd level (3 slots):
conjure animals, glyph of warding, hunger of hadar
4th level (3 slots):
dimension door, evard’s black tentacles, vitriolic sphere
5th level (2 slots):
conjure elemental, teleportation circle
6th level (1 slot):
arcane gate
Wounded Fury. While it has 40 hit points or fewer, the aboleth savant loses its Spellcasting ability, and instead has advantage on attack rolls. In addition, it deals an extra 7 (2d6) damage to any target it hits with a melee attack.
ACTIONS
Multiattack. The aboleth savant makes three tentacle attacks.
Tentacle. Melee Weapon Attack: +9 to hit, reach 10ft., one target.
Hit: 12 (2d6 + 5) bludgeoning damage. If the target is a creature, it must succeed on a DC 14 Constitution saving throw can be removed by any magic that cures disease. After 1 minute, the diseased creature's skin becomes translucent and slimy, the creature can't regain hit points unless it is underwater, and the disease can be removed only by heal or another disease-curing spell of 6th level or higher. When the creature is outside a body of water, it takes 6 (1d12) acid damage every 10 minutes unless moisture is applied to the skin before 10 minutes have passed.
Tail. Melee Weapon Attack: +9 to hit, reach 10ft. one target.
Hit: 15 (3d6 + 5) bludgeoning damage.
Enslave (4/Day). The aboleth savant targets one creature it can see within 60 feet of it. The target must succeed on a DC 17 Wisdom saving throw or be magically charmed by the aboleth until the aboleth dies or until it is on a different plane of existence from the target. The charmed target is under the aboleth's control and can't take reactions, and the aboleth and the target can communicate telepathically with each other over any distance. Whenever the charmed target takes damage, the target can repeat the saving throw. On a success, the effect ends. No more than once every 24 hours, the target can also repeat the saving throw when it is at least 1 mile away from the aboleth.
LEGENDARY ACTIONS
The aboleth savant can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a tim e and only at the end of another creature's turn . The aboleth savant regains spent legendary actions at the start of its turn.
Detect. The aboleth savant makes a Wisdom (Perception) check.
Tail Swipe. The aboleth savant makes one tail attack.
Psychic Drain (Costs 2 Actions). One creature charmed by the aboleth savant takes 14 (4d6) psychic damage, and the aboleth savant regains hit points equal to the damage the creature takes.