Doppelganger

When elves and humans first encountered each other many centuries ago, the elves made a habit of kidnapping humans and replacing them with shape-shifting spies. The practice has since been abandoned, but these "changelings" are still met with suspicion and fear.

Description: You have a favorite form, which you use as your default appearance. You seldom reveal your true form: a pallid elf with onyx eyes and sharply curved ears. Your size is Medium.

Vital Stats: You start with HP 12, SP 3, and MV 6.

Cool and Keen: You gain a boost to Intellect and Will.

Fey Ancestry: You have advantage on all Intellect and Will tests against spells. Your natural life span is very unusual for a Humanoid (about 3,000 years).

Shapeshift (Action): You magically alter your voice and appearance. The transformation doesn't include your belongings, and you must adopt a form that has the same basic arrangement of limbs. Your size can be Medium or Small (see Creature Size and Space), but your other statistics don't change. Otherwise, the extent of the transformation is up to you.

The transformation isn't an illusion, and it lasts until you die or until you dismiss the effect as an action.