D&D 5E Summon Monster Spell

[levimote]

1 minute casting time for a 1 minute concentration spell makes this spell nearly useless for combat. If that's what you intended, cool, but if not reconsider either casting time (1 action) or duration (1 hour concentration).

Good catch! I intended the spell to have a 1 Action casting time. Mistake on my part for not triple proofing.

 

[levimote]

I think 2nd level for 1/2 miiiiiiiiiiiight be fair.

Conjure Animals is Level 3 for 1 CR 2 (and most use it for the multiple of lower levels)
Conjure Minor Elementals and Conjure Woodland Beings is Level 4 for 1 CR 2.
+1 level for double the summons, alongside double the summons for -1 CR, does kind of feel like it should be +1 level for +1 CR.

Following Conjure Minor Elementals and Woodland Beings, Level 2 would be CR 1/2. But, conjure celestial is level 7 for a CR 4, and CR 5 for level 9. This suggests more that +2 spell levels is +1 CR. But it also lasts longer. Conjure Elemental is Level 5 for CR 5, and +1 level for +1 CR, but it can turn on you.

But how much damage can a CR 1/2 monster do in 3 rounds? How much HP does it have? It will function either as a damage spell spread out, a big healing spell (by absorbing a bunch of attacks), or (most likely) a mix of both.

If Conjure Celestial is CR 5 for level 9, and lasts for 1 hour, your Summon Monster is CR 7 for level 9 and lasts 1 minute (I'd drop the casting time to 1 action). That could be fine. Even if you only have 2 combats in 1 hour, that's probably better. Level 7 would allow CR 5, level 7 spell is worth 10 mp and a level 9 is 13 mp, so 2 castings of a 7 is more expensive than 1 of a 9.

Make it 1 action, it's probably balanced. Just check the amount of spells some CR 1 monsters can cast (because if any CR 1 monsters can cast a level 3 spell, it's too much of a trade).

Thanks for the feedback!

CR ½ Monstrosity type creatures

Name Book AC HP AB Dmg Special
Chitine VG 14 18 +4 4 Fey Ancestry, Web Sense, Web Walker
Cockatrice MM 11 27 +3 3 DC 11 Con save x2 or Petrified
Darkmantle MM 11 22 +5 6 Blinds & Suffocates target, Darkness
Piercer MM 15 22 +3 3/10’ Spider Climb, must fall to damage
Rust Monster MM 14 27 +3 5 Rust Metal, Iron Scent
Worg MM 13 26 +5 10 DC 13 Str save or target Prone on bite

Darkmantle and Worg are my favorites here. Rust Monster & Cockatrice could be fun too.

CR 1 Monstrosity Spell-like Abilities
I couldn't find any that actually cast spells, but these have spell-like abilities.

Giant Strider has Fire Burst (Recharges 5-6). The giant strider hurls a gout of flame at a point it can see within 60 feet of it. Each creature in a 10-foot-radius sphere centered on that point must make a DC 12 Dexterity saving throw, taking 14 (4d6) fire damage on a failed save, or half as much damage on a successful one. The fire spreads around corners, and it ignites flammable objects in that area that aren’t being worn or carried.

Harpy has Luring Song. The harpy sings a magical melody. Every humanoid and giant within 300 ft. of the harpy that can hear the song must succeed on a DC 11 Wisdom saving throw or be charmed until the song ends. The harpy must take a bonus action on its subsequent turns to continue singing. It can stop singing at any time. The song ends if the harpy is incapacitated.