Phantom's Exultation

You walk the thin line between the living and the dead. This curse of undeath has also increased your Intelligence, Wisdom, or Charisma score by 1, to a maximum of 20. In addition, you can take a ghastly form as a bonus action, twisting your appearance into a spectral, skeletal aspect. You can do so a number of time equal to your proficiency bonus per long rest. This form lasts for 1 minute, until you drop to 0 hitpoints, or until dropped (no action required). While in this form:

•  Your AC increases by 1
•  You gain a flying speed equal to your walking speed
•  You can move through creatures and objects as if they were difficult terrain. However, if you end your turn inside of a creature or object, you are shunted into the nearest unoccupied space and take 1d10 force damage per 5 feet moved. This damage can not be reduced in any way.