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

(and one other card)

Eldrazi Creature Card with MV=4, 5 or 6

({C} magic symbol) ({C} magic symbol) plus enough mana to pay for the Eldrazi spell available.

Cast an Eldrazi with mana value 4, 5 or 6 from your hand by paying its mana cost.
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.
Resolve the first
Ulalek's trigger, causing you to pay ({C} magic symbol) ({C} magic symbol) 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.
Resolve both Eldrazi cast triggers, if applicable.
Resolve both
Kozilek's Unsealing triggers, creating four 0/1 Eldrazi Spawn creature tokens.
Holding priority, activate two Eldrazi Spawns by sacrificing them, adding ({C} magic symbol) ({C} magic symbol) .
Resolve the copy of
Ulalek's trigger from step 3, causing you to pay ({C} magic symbol) ({C} magic symbol) to copy the Eldrazi spell,
Ulalek's trigger, both
Kozilek's Unsealing triggers and any other abilities on the stack.
Repeat from step 4.