Rule 113.5 · Abilities

Some activated abilities are loyalty abilities. Loyalty abilities follow special rules: A player may activate a loyalty ability of a permanent they control any time they have priority and the stack is empty during a main phase of their turn, but only if no player has previously activated a loyalty ability of that permanent that turn. See rule 606, “Loyalty Abilities.”

Other rules in this chapter

Ask the judge Pro

The life counter has an AI judge that answers your play citing the exact rules. It is part of Gatewatch Pro; the rules, Oracle text and rulings stay free.