What about : your dream self is dead, your dream self from a doomed timeline is in a sprite and you die on your quest bed. What happen ? What would even happen if you die on your quest bed without a dreamself ? Do you just stay dead ?

If you die on a Quest Bed without a Dream Self you just don’t resurrect, you’re just dead. It’s also likely you need to DIE on the Quest Bed, so even if you dragged the body to the Crypt you’d still be unable to Ascend.

Chances are the sprite would work though- Dream Selves operate weirdly outside of the Time-Space Continuum.