Planeswalker cards are permanents you cast during your main phase when the stack is empty, at sorcery speed. When a planeswalker resolves, it enters the battlefield with a number of loyalty counters equal to its printed starting loyalty. You may activate one loyalty ability of each planeswalker you control once per turn, any time you could cast a sorcery. Activating an ability adds or removes loyalty counters as indicated.
Planeswalkers provide reusable effects, often generating card advantage, removing threats, or creating win conditions. They can be attacked by creatures, and damage dealt to them removes loyalty counters. If a planeswalker has zero loyalty counters, it's put into its owner's graveyard. Because they're fragile but powerful, they often draw immediate attention from opponents.
