Spiresignet Dragon

Flying, desertwalk
{u}{r}{t}: You may cast one card with a signet on it without paying its mana cost until end of turn.
{u/r}{u/r}{u/r}{4}: Target opponent discards their hand. You draw a card for every two cards discarded this turn.
It was always there, patrolling the deserts, but no one could know who it was patrolling for... except the Izzet.