TRANSFORMATION. you can cast the Alter Self spell to appear in your second form. When you do so, you gain the effects of that spell’s Change Appearance option and cannot end it to gain the benefits of a different option. Casting alter self in this way requires no spell slot, and you must finish a long rest before you can cast it this way again.
When you cast Alter Self using this feature, some cosmetic aspect of your second form remains after the spell ends. This visibly marks you unless you actively hide or disguise it. The mark fades after you finish a long rest.
INVOLUNTARY CHANGE. Certain circumstances can activate your dark gift. After you experience this catalyst, at the start of your next turn you must succeed on a DC 15 Charisma saving throw or use your next action to cast Alter Self as described in the Transformation trait, even if you have already used it.