Soul Collateral

When a creature within range makes a bargain with you, breaks a promise to you, or drops to 0 hit points while bearing your Pact Mark, bind a debt-fragment. Before the duration ends, spend the fragment to regain 5d8 hit points, gain advantage on one d20 test, or impose disadvantage on one save by the marked creature against your Pact power.

This power has its own stable page so it can be linked from any character, item, location, story post, bargain, curse, or future reward.