606.1
Some activated abilities are loyalty abilities, which are subject to special rules.
Historical Rules · Effective 1 May 2012
Read Section 606 continuously, or open any rule on its dedicated page.
Chapter 6 · Spells, Abilities, and Effects
Section 606
5 rules
Some activated abilities are loyalty abilities, which are subject to special rules.
An activated ability with a loyalty symbol in its cost is a loyalty ability. Normally, only planeswalkers have loyalty abilities.
A player may activate a loyalty ability of a permanent he or she controls any time he or she has priority and the stack is empty during a main phase of his or her turn, but only if no player has previously activated a loyalty ability of that permanent that turn.
The cost to activate a loyalty ability of a permanent is to put on or remove from that permanent a certain number of loyalty counters, as shown by the loyalty symbol in the ability's cost.
A loyalty ability with a negative loyalty cost can't be activated unless the permanent has at least that many loyalty counters on it.