Loyal Demon Dragon

Flying, Indestructible
If there are more than 4 "Loyal Demon" creatures
in your graveyard, you may cast this card without
paying its mana cost.
When Loyal Demon Dragon enters the battlefield,
you may pay {2}{u/b}{u/b}. If you do, destroy all other creatures, artifacts, and enchantments your
opponents control. At the beginning of your end step
you may put a card from your deck into your graveyard, then draw a card.