Dragon Form Mastery

Hexproof
You can't lose the game.
Creatures without flying can't attack you.
At the beginning of each end step, if you've been dealt 5 or more damage this turn, exile Dragon Form Mastery and you lose the game.
{t}: Dragon Form Mastery deals 5 damage to any target. If a creature is dealt damage this way, it deals damage to you equal to its power.