Requires

Scholar of the Lost Trove must be on the battlefield. Helvault must be on the battlefield. Krark-Clan Ironworks must be on the battlefield. Mana needed:

Steps

1. Activate Helvault by paying and tapping it, exiling Scholar of the Lost Trove.
2. Activate Krark-Clan Ironworks by sacrificing Helvault, adding .
3. Helvault leaves the battlefield, returning Scholar of the Lost Trove from exile to the battlefield.
4. Scholar of the Lost Trove enters the battlefield, casting Helvault from your graveyard without paying its mana cost.
5. Repeat.

Results