Gonti's Aether Heart
Whenever Gonti's Aether Heart or another artifact enters the battlefield under your control, you get EE (two energy counters).
Pay EEEEEEEE, Exile Gonti's Aether Heart: Take an extra turn after this one.
I don't think this is a MUD card because it needs another 3 artifacts AFTER it hits play, so it really wouldn't work. Unless there's a MUD Energy deck to be made, with Aetherworks Marvel (I doubt it).
But would Paradoxical Outcome be glad with extra turns? I bet this is easy enough to trigger with an Outcome, but so is anything else I guess. I think this is better than Paradox Engine in that kind of deck though.