Originally Posted by
Prince Zahn
capstone... perhaps Something like: "at 20th level, you can form a pact with a trusted vestige that last indefinitely. If you do so, the vestige remains in your body until you renegotiate the bound pact. You can only have one vestige bound in this fashion at once."
Just a suggestion :3 it's a little bit of a "safety net" feature, you might make it along the lines of Signature Spell (wizard), at-will wild shape (druid) or starting every combat with Ki Points (Monk).