Cast Spawn-Gang Commander by paying {3}{R}{R}.
Ulalek and Spawn-Gang Commander trigger twice, and Echoes of Eternity triggers once.
Resolve the Echoes of Eternity trigger, copying the Spawn-Gang Commander spell.
Resolve the copy of the Spawn-Gang Commander spell.
Resolve one of the Spawn-Gang Commander triggers from step 2, creating three 0/1 Eldrazi Spawn creature tokens.
Activate two Eldrazi Spawn creature tokens by sacrificing them, adding {C}{C}.
Resolve the copy of Ulalek's trigger, causing you to pay {C}{C} to copy the Spawn-Gang Commander spell, Ulalek's trigger and Spawn-Gang Commander's trigger.
Repeat from step 4.

Infinite colorless mana

Infinite copies of abilities you control on the stack

Infinite creature tokens

Infinite damage

Infinite death triggers

Infinite creature ETB

Infinite creature LTB

Infinite creature sacrifice triggers

Ulalek, Fused Atrocity

Echoes of Eternity

Spawn-Gang Commander

Cast Spawn-Gang Commander by paying {3}{R}{R}.
Ulalek and Spawn-Gang Commander trigger.
Holding priority, activate Strionic Resonator by paying {2} and tapping it, copying Ulalek's trigger.
Resolve the copy of Ulalek's trigger, causing you to pay {C}{C} to copy the Spawn-Gang Commander spell, then Ulalek's trigger and Spawn-Gang Commander's trigger.
Resolve the copy of Spawn-Gang Commander's trigger, creating three 0/1 Eldrazi Spawn creature tokens.
Activate two Eldrazi Spawn creature tokens by sacrificing them, adding {C}{C}.
Repeat from step 4 any number of times.
Once you have infinite {C} and Eldrazi Spawn tokens, you may sacrifice them to Spawn-Gang Commander to deal infinite damage to any target(s), and you may resolve all copies of the Spawn-Gang Commander spell.

Strionic Resonator

Cast Spawn-Gang Commander by paying {3}{R}{R}.
Ulalek and Spawn-Gang Commander trigger.
Holding priority, activate Lithoform Engine's first ability by paying {2} and tapping it, copying Ulalek's trigger.
Resolve the copy of Ulalek's trigger, causing you to pay {C}{C} to copy the Spawn-Gang Commander spell, Ulalek's trigger and Spawn-Gang Commander's trigger.
Resolve the copy of the Spawn-Gang Commander spell.
Resolve the copy of Spawn-Gang Commander's trigger, creating three 0/1 Eldrazi Spawn creature tokens.
Activate two Eldrazi Spawn creature tokens by sacrificing them, adding {C}{C}.
Resolve the copy of Ulalek's trigger from step 4, causing you to pay {C}{C} to copy the Spawn-Gang Commander spell, Ulalek's trigger and Spawn-Gang Commander's trigger.
Repeat from step 5.
Once you have infinite {C} and Eldrazi Spawn tokens, you may sacrifice them to Spawn-Gang Commander to deal infinite damage to any target(s).

Lithoform Engine

Cast Spawn-Gang Commander by paying {3}{R}{R}.
Ulalek triggers twice, and Spawn-Gang Commander triggers once.
Resolve one of Ulalek's triggers, causing you to pay {C}{C} to copy the Spawn-Gang Commander spell, Ulalek's trigger and Spawn-Gang Commander's trigger.
Resolve the copy of Spawn-Gang Commander's trigger, creating three 0/1 Eldrazi Spawn creature tokens.
Holding priority, activate two Eldrazi Spawns by sacrificing them, adding {C}{C}.
Resolve the Ulalek trigger from step 3, causing you to pay {C}{C} to copy the Spawn-Gang Commander spell, Ulalek's trigger and Spawn-Gang Commander's trigger.
Repeat from step 4.

Combos with "Spawn-Gang Commander"