people from across the multiverse are pulled into a pocket dimension where they must survive, and they are given the ability to fuse with one another(two people fusions only), downside? you can only unfuse if you have trust in each other and achieve a stable state of mind(fusions function as steven universe type, both components minds exist secondary to a new mind upfront)

Dangers of Fusion- the point would be easier to make with Steven Universe fusion in this part, the fusion has its own identity and personality independent of those fusing together, they(the fusion) have a desire and wants, to the point that when they unfuse, they basically disappear, which is a terrifying concept, imagine your a fusion(the personality and identity depend of your parts) and your components want to unfuse, they are basically saying they want you to disappear so they can be there individuql selves again, saying you need to fade away and disappear, without know if you'll ever be needed again, to never know if you'll exist every again is a terrifying thought that makes me wonder why they haven't shown this side of the argument in fusions, they have in SU with Sugulite(voiced by Nicki Minaj) who didn't want to unfuse due to, and I Quote "it feels so good to be me" when pearl says they've lost themselves, its basically Garnet and Amethyst were holding Sugulite back to keep her from keeping the fusion together, but sugulite broke free and basically trapped Garnet and Amethyst inside her, because she didn't want to disappear and cease to exist, a pretty terrifying concept when you think about it, and makes the idea seem very dangerous and risky.

if the components of the fusion dislike each other, the fusion itself would possibly be Suicidal and try to unfuse despite the components trying to stay together