Cast Turnabout targeting yourself naming untap lands, hold priority.
Activate Mirror Sheen to copy Turnabout.
Let the copy resolve, choosing to untap.
Repeat.

Infinite colored mana

Infinite colorless mana

Turnabout

Mirror Sheen

Cast Lava Spike, targeting yourself.
Splice Desperate Ritual onto Lava Spike.
Hold priority and activate Mirror Sheen, targeting Lava Spike.
Have the copy of Lava Spike target another player.
Resolve the copy of Lava Spike.
Using the RRR from the copy of Lava Spike's text from Desperate Ritual, activate Mirror Sheen, targeting Lava Spike.
Repeat.

Combos with "Mirror Sheen"