Activate any number of creatures you control by tapping them, adding at least {5}{G}.
Activate Isochron Scepter by paying {2} and tapping it, casting a copy of Vitalize without paying its mana cost.
Resolve Vitalize, untapping all creatures you control.
Activate Elder Druid by paying {3}{G} and tapping it, untapping Isochron Scepter.
Repeat.

Infinite storm count

Infinite untap of creatures you control

Infinite mana creatures you control can produce

Infinite magecraft triggers

Isochron Scepter

Elder Druid

Vitalize

Activate Magosi's second activated ability by tapping it and paying {U}.
Rings of Brighthearth triggers; choose not to pay for it.
Resolve the Magosi ability, putting an eon counter on Magosi and skipping your next turn.
Activate Elder Duid by paying {3}{G} and tapping it, targeting Magosi.
Rings of Brighthearth triggers; choose not to pay for it.
Activate Magosi's third activated ability by tapping it, removing an eon counter from it, and returning it to your hand.
Rings of Brighthearth triggers; pay {2} and copy the Magosi ability.
Resolve both copies of the ability, cancelling out your skipped turn and taking an extra turn after this one.
Play Magosi.
Repeat each turn.

Infinite turns

Magosi, the Waterveil

Rings of Brighthearth

Combos with "Elder Druid"