Unbreakable Promise

You need to cut your hand and take a thing that represents someone in your bleeding hand. After this you need to say a positive or negative promise for that person in the company of two witnesses. As long as the promise binds you you will have that scar on your hand. The promise needs to be executed in 10 days, your promise can't surpass the time leght but you can describe limitations such: "I will help you to earn the gold you need tomorrow." Or: "If you are one mile close My Dear, I'll find you." - If the promise is not accomplished in the described circumstances the one who made it must throw a WIS save against it's own spell save DC, on failure suffers 4d20 psyhic damage, on success half that value, if you did anything for the sake of your success, but you still failed to accomplish you suffer halfed damage. To reach the described goal you have advantage on your checks and actions that serve the accomplishment. If you made a promise against one named enemy (and can be only one at the time) like this: "Zeradas you demon, I'll take my revenge on you!" you have advantage on attack rolls against that enemy hand have advantage on saves and effects against that your enemy does. Only one Unbreakable Promise can be active at the same time.

A creature can realize by an insight check against your spellcasting modifier DC or with spells such detect magic that you made a promise targeting them. If its an enemy who wants to break the promise on itself it can throw a CHA save against your spell save DC every morning for the spell's duration, or use dispel magic to end the promise. You know if they succeed to break your promise bacause the scar dissapears in that moment they done it.