Originally Posted by
Gypsy
Planewalker is a newer card type. You cast them like anything else and they stay on the board (see: a permanent). The number in the lower right is his loyalty counter or basically health. If it gets to zero or below he dies. He can be attacked like a player. Damage dealt to a player via a spell can be redirected to one planewalker that player controls.
The abilities add or subtract loyalty counters. You can't use a subtracting ability to take a planewalker below zero. Or in Jace's special awesome case he can just Brainstorm for free every turn with his 0 ability. This is probably his most common use because it's inherent card advantage which is more or less what wins games of Magic. He's also a win condition in and of himself if you can stall out the game (or take infinite turns). You simply +2 him until you can ultimate twice which ends the game.
Short version: he also has secret text that is written in invisible ink. It reads: If Jace resolves you win the game.
