Balatro

I tried to make it clear enough with the limited typing space you'd get, but that leaves out a lot of the tangential info of course. When I say Joker chips and mult can't decrease, think about the many cards which offer an unconditional trigger of these things in a given hand. When the trigger is unconditional, there tends to be an external condition which needs to be fulfilled, which can either decrease or reset (e.g. Hit The Road Jack, Ride The Bus). A joker can also be perishable and lose chips and mult over time (e.g. Popcorn, Ice Cream). Ain't Goin Nowhere would effectively prevent any of these from providing less than the maximum mult they've given since when this Joker was added to your run.

An important note though would be that these cards would still both perish and reset or decrease as normal, but would never provide that lower value, instead waiting for you to meet the conditions to increase it beyond your current maximum.

The second aspect of the Joker is that you cannot sell other jokers (as in, only this Joker can be sold while it's in play). This is functionally related to ratcheting down everything, and also a penalty to work around if you want to try and work with the potentially quite powerful effect. If you have fewer than the maximum amount of Jokers, you can buy more, but once bought, they are stuck there unless they either perish or are destroyed (e.g. Gros Michel, Ceremonial Dagger). You need to be mindful of anything you pick up, or you'll have to sell this card and change your strategy.

The best time to get this card would likely be once you have some established Jokers, and a rare conditional xMult card (e.g. Campfire) or an economy card like Bull or Bootstraps. Something that has synergy in a way where you can just massively inflate it and lock it in for the rest of the run. Verdant Leaf would destroy you though.