Onslaught

When Goblin Pyromancer enters the battlefield, Goblin creatures get +3/+0 until end of turn. At the beginning of the end step, destroy all Goblins.

{T}, Pay 1 life, Sacrifice Bloodstained Mire: Search your library for a Swamp or Mountain card, put it onto the battlefield, then shuffle.

{5}{R}{R}: Create a 5/5 red Dragon creature token with flying. (It can't be blocked except by creatures with flying or reach.)