Are the Summon Monster Tables set in stone?

[Snow Savant]

Try this correllation for matching up legal extraplanar or elemental creatures to their corresponding SM/SNA spell:

SM/SNA Spell >>> CR
================
1 > Less Than 1
2 > 1
3 > 2
4 > 3
5 > 4-5
6 > 6-7
7 > 8-9
8 > 10-11
9 > 12-13

Elementals get favorable treatment on the SNA list, with a 1 level delay on the SM list (since they get the extraplanar creatures).

Feel free to use the MotP templates to make new creatures into elementals/extraplanars so they become legal for the SM/SNA spells. This will greatly expand your selection of creatures to be summoned.

In addition, if you can summon a Celestial Bison, you sure as heck can also summon a Fiendish, Axiomatic, or Anarchic one as well.

Note, books like BoED and FF add more creatures to the SM list, implying that the PHB tables are indeed good "starting off" reference points for the Summoning spells. Many other quality D20 monster books also expand the Summoning options as well.

Hope that helps.

XO,
Snow

 

[Olive]

Try this correllation for matching up legal extraplanar or elemental creatures to their corresponding SM/SNA spell:

SM/SNA Spell >>> CR
================
1 > Less Than 1
2 > 1
3 > 2
4 > 3
5 > 4-5
6 > 6-7
7 > 8-9
8 > 10-11
9 > 12-13

This is basically the Dragon mag method. But I added a Advespa Devil (MM2, CR3) and it was way too overpowered for a SMIV, so it's not always perfect.

 

[Brother MacLaren]

In addition, if you can summon a Celestial Bison, you sure as heck can also summon a Fiendish, Axiomatic, or Anarchic one as well.

It might not be unbalancing to allow a caster to apply whatever template they want to summoned creatures, but it does increase the power of the spell. The summon spells aren't overpowered, so a little boost probably isn't out of line. But it's the kind of thing where the DM should actively decide "Yes, I want to boost the summon spells a bit." The player shouldn't try to argue "It's no difference at all."
By allowing template switching, you suddenly give the good cleric access to a lot of poisonous creatures he didn't have before - an advantage against some foes. He also gets a creature with reach (ape) at SM3, and access to constrictor snakes (very useful in some cases). Likewise, you give the evil cleric a few more options for flying creatures, as well as some more trampling creatures (good against hordes of little guys). If you allow not just a static change to the list but unlimited template switching on-the-fly, then the summoner can better deal with foes of known alignment. Fighting slaadi? Summon the axiomatic versions. Fighting an illithid? Try celestial or anarchic.
It isn't necessarily a huge power boost, but it definitely is something that the DM would have to approve.

 

[Gez]

This is basically the Dragon mag method. But I added a Advespa Devil (MM2, CR3) and it was way too overpowered for a SMIV, so it's not always perfect.

Well, that table is only a guideline.

There are other parameters.

If the monster can do non-hit-point damage (for example, it has ability poison, or ability drain): then bump its summon level by one point, maybe even two if it can do level drain.

If the monster can have the caster benefit from the spell of level X: then the summon level must be at least X+1, bump it accordingly otherwise. Don't necessarily do that if the spell-casting or spell-like ability is limited (like formian workers that must be several to cast make whole or heal, or efreet that can cast wish only once in a long while).

 

[Olive]

The other probelm is if you give alignemnt templates then why not elemental ones too? the tremorsense of an earth elemental dog is a pretty powerful tool at the right time.

O the advespa, I suspect the CR is actually too low for the creature anyway, hence the problem.

 

[Voadam]

Avatar's handbook gives some guidelines for what levels the creatures in there can be summoned and Book of Fiends they are planning a web enhancement for the same.