I can't think of a power that feels right

So certain people have authorities so a full authority is complete control of something like if you had the full authority of ice you could create and manipulate ice

You could have a partial authority that are powers with conditions like you grow stronger the longer you fight

Or a land authority that lets you control certain land

The MC has the full authority of deals and the main power is to make unbreakable deals

I either need to give them more abilitys or change their authority to something that still includes the main ability

I need to do this to balance them with people who can cut someone in half, someone who creates tornadoes and people who can create mountains of ice

I don't really want to give them combat abilities and I want it to feel like making a deal with the devil. I don't want to give them mind control or slavery magic

So I'm asking if you have any ideas

Note: someone can't have two authorities regardless of type they can only have one

Edit The MC is a prince and I'm trying not to make them a Mary sue who can do anything.

The story follows them as they try to get revenge on their family for disowning him

Their power should play into his cleverness

So far the very basic outline I have is 1he is disowned 2 he makes a deal with a merchant for them to buy up a lot of food and hold it for him creating an artificial scarcity 3 he through some means gets a hot spring or bath house to be renamed to the fountain of youth 4 he visits a bordering kingdom with a king obsessed with not dying and tells him that he knows where the fountain of youth is and will let them bathe in it if they go to war with his home national 5 he hands out food building his support

At some point Early on he meets a older knight with a partial authority that makes her stronger. She was banished by her Lord's son because she hit him after he hit a child She is around fifty years old, black woman, and while her strength is starting to fade her authority keeps her in good shape, she has a very motherly Vibe. She joins the MC because one he is still a child and two he promised to create better conditions for children

By unbreakable I don't mean you can't break the deal. I mean you die if you break it unless there's a stipulation that changes the punishment death is

the default