Invocation Adept

Through the devout studies of both occult lore and occult relics, you have attained some eldritch power within yourself: you learn one Eldritch Invocation option of your choice from the warlock class. If the invocation has a prerequisite, you may choose that invocation as long as you are a warlock who meets the prerequisite.

Whenever you gain a level, you can replace the invocation with another one from the warlock class.