changeling nature mastery

the extensive practice of your changeling nature to transform into other humanoids as taken a new level, you can now transform in creatures other than humanoids

• starting at level 4 : you gain the ability to morph into a humanoid one time bigger or smaller than you, you can also transform into a fiend or any creature you have seen of a CR max 1\4 without flying, climbing or swimming speed. once you use this feat you can't use it again before doing a long rest.
• starting at level 8: you can now morph into a creature of CR max 1\2 (no flying speed), you can only use this feat once per long rest.
• starting at level 12 you can now transform into a creature max CR 1, you can use this feat twice per day, gaining any expended use after a long rest
• starting at level 16 you can now morph in any creature max CR 4 and size small to large, you regain this ability every short rest
• At level 20 you can now cast verbal and somatic components of any class spell you might have when transformed into something that wouldn't normally be allowed to. while transformed in this way you use your charisma to cast your spells,  you can morph into any Creature of CR 6 and lower, size small to large, you can use this ability twice and regain it every short rest

these transformation are similar to a druid use of wild shape:

• Your game statistics are replaced by the statistics of the beast, but you retain your alignment, personality, and Intelligence, Wisdom, and Charisma scores. You also retain all of your skill and saving throw proficiencies, in addition to gaining those of the creature. If the creature has the same proficiency as you and the bonus in its stat block is higher than yours, use the creature’s bonus instead of yours. If the creature has any legendary or lair actions, you can’t use them.
• however, you keep any hitpoints you previously had, falling inconscious  and reverting to your normal form if you drop to 0.
• in combats transforming into something is an action while reverting to your normal form can be done as a bonus action