Dreamscape game
Torg could be tweaked to fit what you're talking about. Don't ask me how though, I've never too terribly into Torg.
Likewise if you're up to it, FATE or Amber Diceless/Lords Of Gossamer And Shadow. FATE Core is more of a toolbox, the system is genre agnostic (it's geared toward Narrative style play, rather than tactical/simulation) so you can literally do what you want with it.
Amber has a setting implied not only in the setting, but the rules. Whereas Lord Of Gossamer and Shadow, despite having a setting, is much easier to adapt the powers to fit a different genre/setting. They're the same rulesets, they just have different settings.
You might also look into Godbound. It's not really what you're talking about, but you might be inspired to mod it to fit.