You have refined your Changeling Change Appearance ability to the point where you can mimic some features of the races you change to.  Once per long rest, when you assume the form of a player race using Change Appearance, you may choose one of the following traits to copy from it, assuming that race normally grants the chosen trait:

• Darkvision out to 60 feet.
• A single type of damage resistance.
• Advantage against a specific type of save, such as the Fey Bloodline advantage against Charm saves.
• A single specific weapon or armor proficiency granted by that race.
• The ability to trance instead of sleeping; choosing this option also grants immunity to magical sleep effects.
• Any one limited-uses-per-rest (short or long) ability granted by that race, such as a Dragonborn's breath weapon.  If the ability has a level requirement, you must be of the appropriate character level.

Until your next long rest, you have the chosen trait while in any form that could grant it, and cannot use this ability to gain any other traits.

If the racial trait you copy has a limited number of uses, the limit is tracked regardless of how often you change form, and resets (if appropriate) when you rest regardless of whether you are in the appropriate form to use it or not.

Adapated from Bloodline Mimickry by Aquillion