In Dungeons & Dragons, many sentient beings or devices could learn spells &/or rituals. But it's unclear who is able is able to perform somatic components normally done by a humanoid of 3' to 6' height. For example, these concern me:
- Oozes: they're, well, oozes. Can they perform spell gestures? If they're ambulatory and have pseudopods, is that enough?
- Fae: if they're only 3" tall (6-7 cm) are their hands still large enough?
- Magic items & animated parts: would an animate embossed cameo within a ring, necklace or coin be enough?
- Sentient and Awakened creatures: octopi, trees, wolves or squirrels: do paws, branches & tentacles count?
- Do gesturing images within mirrors (possibly up to full humanoid size) also count?
- Handicapped: how many fingers/thumbs can one lose and still cast spells?
- Is giving this ability to illusions, be they permanent, programmed or projected, a logical yet terrible precedent?
Obviously these are all answered just by knowing how much one needs move to trigger somatic components. I cannot find this answer, even in previous versions of D&D.
All these concerns do, in the end, lead to the following question: What appendages does any monster need to provide somatic components for its spells?