Activate Anzrag by paying {3}{G}{G}{R}{R}, causing opponents to block Anzrag if able this turn.
Cast Darksteel Mutation for {1}{W} targeting the only creature an opponent controls.
Resolve Darksteel Mutation, turning the enchanted creature into a 0/1 Insect artifact creature with indestructible.
Declare Anzrag as an attacker, attacking the opponent who controls the enchanted creature.
The opponent is forced to block Anzrag with the enchanted creature, triggering Anzrag, untapping all creatures you control and causing you to get an additional combat phase after this one.
Repeat from step 4.

Infinite combat phases

Infinite untap of creatures you control

Infinite mana creatures you control can produce

Anzrag, the Quake-Mole

Darksteel Mutation

Deal combat damage using Medomai, triggering its ability, causing you to take an extra turn after this one.
During your extra turn, cast Darksteel Mutation by paying {1}{U}, attaching it to Medomai.
Declare Medomai as an attacker, as it does not have its restriction due to Darksteel Mutation.
Holding priority, cast Capsize with buyback by paying {4}{U}{U}, returning Darksteel Mutation and Capsize to your hand.
Repeat from step 1.

Combos with "Darksteel Mutation"