An immortal who changes reality with words that have to make sense - to me, this sounds too close to being a Dungeon Master. And there can be only one.

Besides, how do you tone it down? Such a character would literally have an infinite amount of solutions to any problem. How do you challenge them? How do you force them into a corner? How do you create a story that makes sense when one of the character has a power that can change the plot directly?

One of the characters in this game has an ability to change their material composition to anything they touch, while, I assume, retaining their ability to move and think. This ability is very powerful, but can be toned down and limited, because it lives within a very specific frame. But, yknow, "change anything and never die"? I am trying hard to be polite here. The restriction in my eyes is fictive. They can basically attempt [i]anything[/i], and it can either work or not. Nobody should be able to attempt anything with a chance of success that isn't zero.