Ulalek, Fused Atrocity, Echoes of Eternity, and Kozilek's Unsealing

Prerequisites

• Ulalek, Fused Atrocity on the battlefield
• Echoes of Eternity on the battlefield
• Kozilek's Unsealing on the battlefield
• plus enough mana to pay for the Eldrazi spell available

Steps

1. Cast an Eldrazi with mana value 4, 5 or 6 from your hand by paying its mana cost
2. Ulalek and Kozilek's Unsealing's first ability trigger twice, the Eldrazi cast triggers twice if it has a cast ability, Echoes of Eternity triggers once if the Eldrazi cast was colorless
3. Resolve the first Ulalek's trigger, causing you to pay to copy the Eldrazi spell, Ulalek's trigger, both Kozilek's Unsealing triggers, both Eldrazi cast triggers if it had one, and the Echoes of Eternity trigger if it triggered
4. Resolve both Eldrazi cast triggers, if applicable
5. Resolve both Kozilek's Unsealing triggers, creating four 0/1 Eldrazi Spawn creature tokens
6. Holding priority, activate two Eldrazi Spawns by sacrificing them, adding
7. Resolve the copy of Ulalek's trigger from step 3, causing you to pay to copy the Eldrazi spell, Ulalek's trigger, both Kozilek's Unsealing triggers and any other abilities on the stack
8. Repeat from step 4

Results

• Infinite colorless mana
• Infinite copies of abilities you control on the stack
• Infinite copies of the cast Eldrazi
• Infinite creature tokens
• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinite sacrifice triggers