Holoshifter (5e Feat)
From D&D Wiki
Prerequisites: You must be a Gem.
You have learned how to manipulate your projected form into that of other creatures. As an action, you can assume the form, appearance, size, and shape, but not coloration or voice, of any creature you have seen before. You will gain this creature’s size and physical abilities, such as winged flight or claws, but not magical race traits, proficiencies, ability scores, or legendary actions. The shapeshift may be held for 10 minutes and takes your concentration, though this time is halved for every size class the creature is above your own. You may use this ability twice and regain all uses on a long rest.