Cloudstone Curio + Phyrexian Altar + Underworld Hermit

Cloudstone Curio

Phyrexian Altar

Underworld Hermit

How it works

1. Cast Underworld Hermit by paying 4.
2. When Underworld Hermit enters the battlefield, it and Cloudstone Curio trigger.
3. Resolve the Cloudstone Curio trigger, choosing to return nothing to your hand from the battlefield.
4. Resolve the Underworld Hermit trigger, creating a number of 1/1 Squirrel creature tokens equal to your devotion to black.
5. When the Squirrels enter the battlefield, Cloudstone Curio triggers that many times.
6. Resolve the first Cloudstone Curio trigger, returning Underworld Hermit to your hand from the battlefield.
7. Resolve all remaining Cloudstone Curio triggers, choosing to return nothing to your hand from the battlefield.
8. Activate Phyrexian Altar six times by sacrificing six Squirrels, adding 4.
9. Repeat.
10. If your devotion to black excluding Underworld Hermit is at least five, this combo will net infinite colored mana.