Shapechanger: counts as a shapechanger, which renders it immune to polymorph and gives it disadvantage vs. moonbeam.
Changeling Instincts. You gain proficiency with two of the following skills of your choice: Deception, Insight, Intimidation, and Persuasion.
Change Shape: (action) change appearance and voice, coloration, hair length, sex, height and weight, race, [not game statistics, or gear] only the appearance of a creature you've seen (small or medium) with the same basic arrangement of limbs. You stay in the new form until you use an action to revert to your true form or until you die.
Gains Mastery: at level 3 the changeling can now transform into small and large humanoids
Elastic Face: at level 10 the Changeling learns how to change into completely new creatures. (removes the only creatures you've seen before limitation)