Astéri, World Ender

Costs {x} less to cast, {x} = # of dinosaurs in play. Whenever a dinosaur leaves the battlefield, create Fossil tokens {s} = to total mana cost Power and toughness = {s}, unblockable, vigilance
ETB: Destroy all dinosaurs and then deal {s} to all creatures not under your control.
Extinction {r}{g}{w}: Deal {s} player damage up to 3 opponents and then sacrifice fossil tokens {s} equal
to 1/2 rounded down.