Bladewing's Thrall + Cloudstone Curio + Slumbering Dragon + Phyrexian Altar

Bladewing's Thrall

Cloudstone Curio

Slumbering Dragon

Phyrexian Altar

How it works

1. Cast Slumbering Dragon by paying .
2. When Slumbering Dragon enters the battlefield, Cloudstone Curio and Bladewing's Thrall trigger.
3. Resolve the Cloudstone Curio trigger, choosing to return nothing to your hand.
4. Resolve the Bladewing's Thrall trigger, returning it from your graveyard to the battlefield.
5. When Bladewing's Thrall enters the battlefield, Cloudstone Curio triggers, returning Slumbering Dragon from the battlefield to your hand.
6. Activate Phyrexian Altar by sacrificing Bladewing's Thrall, adding .
7. Repeat.

This loop is a masterclass in recursive recycling, using Cloudstone Curio as the heartbeat of the engine whenever a creature enters the battlefield. By casting Slumbering Dragon to trigger the Curio, you can let Bladewing's Thrall slide back onto the battlefield from your graveyard; since the Thrall is a Dragon, it conveniently satisfies its own resurrection condition while simultaneously triggering the Curio to bounce the Slumbering Dragon right back to your hand. From there, Phyrexian Altar steps in to convert Bladewing's Thrall into the exact red mana needed to recast the Slumbering Dragon and start the whole dance over again.