Worldgorger Dragon | Molten Echoes

Cards

Molten Echoes on the battlefield.
Worldgorger Dragon in hand.
"Dragon" chosen with
Molten Echoes.
({3} magic symbol) ({R} magic symbol) ({R} magic symbol) ({R} magic symbol) available.

Cast
Worldgorger Dragon, triggering
Molten Echoes and
Worldgorger Dragon's ETBs; stack the triggers to resolve in that order.
Resolve
Molten Echoes' trigger, creating a token copy of
Worldgorger Dragon and triggering its ETB.
Float as much mana as you want in response to the token's ETB trigger.
The token's effect resolves, exiling everything else you control, including the original
Worldgorger Dragon.
Resolve the original
Worldgorger Dragon's LTB with no effect, then resolve the ETB trigger of the original
Worldgorger Dragon, exiling the token copy.
Resolve token
Worldgorger Dragon's LTB trigger, returning everything it exiled to the battlefield under your control.
Name Dragons as
Molten Echoes enters the battlefield.
Repeat the loop from the top for infinite mana.
Repeat this process until you have infinite mana.
The loop can broken by naming a different creature type as
Molten Echoes enters the battlefield.