In my game the character's powers stem from a contract with a supenatural entity called a CARD (mainly because I have nothing else to call it right now), I'm currently debating whether or not to make a system revolving around making a contract or to just leave it in the background.

If I make a mechanic for it it'll probablly have four contracts linked to the suits in tarot, the type of contract might give a little boost or something but mainly be for flavor, in that case the contracts will be as follows;

Contract of Pentacles: The user specificlly preforms some ritual to summon & make a contract with a CARD.

Contract of Cups: The CARD searches out the user for whatever reason and then has to convince the user to agree.

Contract of Rods: The user experience some event in their life where it's either do the impossible or die, their spirit "flares" attracting a CARD like a moth to a flame.

Contract of Swords: The CARD's power is sealed within the user's body, whether caused by somebody else or from the user accidently touching the wrong object.

I just came up with these more or less off the top of my head so any alternative suggestions are appreciated, as for questions,
Does this make sense?
Should I include this mechanic at all or just leave it in the background?
What type of bonuses /  penalties should come from each contract?
Should I put how exactly the contract is actually made instead of the events surrounding it?
Should I have more then just the four types of contracts?