When I first started to write the post to go with this example, I gave up almost immediately, typed (nope) as a placeholder, and went on to the next one. Sometimes, even this Wielder of the Red Pen of Doom (DOOM, I tell you!) can’t face any more wonky sentence structures…
Change the first sentence to this: You are an ancient evil, sealed away in a treasure-filled vault that can be opened only by solving a puzzle, which will remove the magic seal.
(I got rid of the last bit because there’s no way to know what the author intended to say — I suspect there’s a homophone glitch/misinterpretation lurking there — and I don’t have the mental energy to bother with it right now.)
The second sentence is fine as it is.