Cloudstone Curio + Phyrexian Altar + Abhorrent Overlord

Cloudstone Curio

Phyrexian Altar

Abhorrent Overlord

How it works

1. Cast Abhorrent Overlord by paying 5.
2. When Abhorrent Overlord 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 Abhorrent Overlord trigger, creating a number of 1/1 Harpy creature tokens equal to your devotion to black.
5. When the Harpys enter the battlefield, Cloudstone Curio triggers that many times.
6. Resolve the first Cloudstone Curio trigger, returning Abhorrent Overlord 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 seven times by sacrificing seven Harpys, adding 5.
9. Repeat.
10. If your devotion to black excluding Abhorrent Overlord is at least six, this combo will net infinite colored mana.