Give Forerunner of the Empire indestructible by any method.
Cast Polyraptor by paying {6}{G}{G}.
Polyraptor enters the battlefield, triggering Forerunner of the Empire, causing it to deal 1 damage to each creature.
All Polyraptor creatures trigger.
Resolve one Polyraptor trigger, creating one token copy of Polyraptor.
Repeat from step 3 any number of times.
End the loop by declining to deal damage with Forerunner of the Empire triggers and resolving an arbitrarily high number of Polyraptor triggers.

Infinite creature tokens

Infinite damage to all creatures

Infinite death triggers

Infinite creature ETB

Infinite creature LTB

Polyraptor

Forerunner of the Empire

Deal damage to Polyraptor.
Rite of Passage and Polyraptor trigger.
Resolve the Rite of Passage trigger, putting a +1/+1 counter on Polyraptor.
Resolve the Polyraptor trigger, creating a token copy of it.
The Polyraptor token enters the battlefield, triggering Forerunner of the Empire's second ability, dealing 1 damage to each creature.
Rite of Passage triggers for each creature you control, and each Polyraptor you control triggers.
Resolve all Rite of Passage triggers, putting a +1/+1 counter on each creature you control.
Resolve a Polyraptor trigger, creating a token copy of it.
Repeat from step 5.

Infinite damage to creatures

Infinite +1/+1 counters on creatures you control

Rite of Passage

Cause a Dinosaur to enter the battlefield under your control.
Forerunner of the Empire's second ability triggers, dealing 1 damage to each creature.
Raptor Hatchling triggers, and Rite of Passage triggers for each of your creatures dealt damage this way.
Resolve all Rite of Passage triggers, putting a +1/+1 counter on each creature you control.
Resolve the Raptor Hatchling trigger, creating a 3/3 Dinosaur creature token.
Repeat from step 2.

Raptor Hatchling

Deal damage to Polyraptor.
Polyraptor triggers, creating a token copy of it.
The Polyraptor token enters the battlefield, triggering Forerunner of the Empire's second ability and Cathars' Crusade.
Resolve the Cathars' Crusade trigger, putting a +1/+1 counter on each creature you control.
Resolve the Forerunner of the Empire trigger, dealing 1 damage to each creature.
Each Polyraptor you control triggers.
Resolve a Polyraptor trigger, creating a token copy of it.
Repeat from step 3.

Combos with "Forerunner of the Empire"