The first time you cast Uro, you pay 3 mana for 3 points of life and a card draw. That's not bad, but this card also has Escape, a brand-new mechanic, which costs 4 mana and 5 exiled cards. It returns as a 6/6 creature and can return again and again.
Obviously, you need a ton of discard spells to sustain Uro. But with its card draw triggers, including one with each attack, this is one of the most broken cards in Theros Beyond Death.