Sun Titan + Animate Dead + Necromancy + a sacrifice outlet = infinite sacrifices and ETBs
How it works:
- Have Sun Titan in your graveyard
- Cast either Animate Dead, targeting Sun Titan
- Sacrifice Sun Titan
- Cast Necromancy, targeting Sun Titan
- Target Animate Dead with Sun Titan's ETB ability
- In response, sacrifice Sun Titan
- Return Sun Titan to the battlefield with Animate Dead
- Repeat