I'm just getting access to the Polymorph spell this level, and I'm curious about beasts with innate capabilities. Swarm of Cranium Rats (CR5) are probably the strongest example:
Innate Spellcasting (Psionics). The swarm’s innate spellcasting ability is Intelligence (spell save DC 13). As long as it has more
than half of its hit points, it can innately cast the following
spells, requiring no components:At will: command, comprehend languages, detect thoughts
1/day each: confusion, dominate monster
Do you have access to a monster's innate capabilities while you are polymorphed into them? I'm interested in learning the answer for all monster traits in general, but I'm particularly focused on spellcasting.
Best Answer
You can use a beast's innate abilities while Polymorphed (but you probably can't Polymorph into a swarm of beasts)
Polymorph states that:
And as the guidance on reading monster entries indicates, a monster's game statistics are everything in its stat block, which includes any special actions available to the monster and special traits it has. If a beast has an innate property like spellcasting or darkvision or telepathy, it is available for you to use when polymorphed.
However, you may have the problem in your specific example of becoming a swarm of cranium rats, because Polymorph allows you to assume the form of "a beast", singular - and a swarm is a collection of many beasts, as explored a little in this question about wild shape and swarms.