Sun Titan + Unhallowed Pact + sacrifice outlet = infinite sacrifices and ETBs
How it works:
- Have Sun Titan enchanted with Unhallowed Pact and a sacrifice outlet on the battlefield
- Sacrifice Sun Titan, then return it to the battlefield with Unhallowed Pact's triggered ability
- Return Unhallowed Pact to the battlefield with Sun Titan's ETB trigger, enchanting Sun Titan
- Repeat