Rules glossary
↑ Parent rule: 116.2 There are twelve special actions:
116.2m A player who controls a permanent that has one or more locked halves (see rule 709.5) may pay the mana cost of a locked half of that permanent to give that permanent the appropriate unlocked designation. This cost is referred to as an “unlock cost.” A player can take this action any time they have priority and the stack is empty during a main phase of their turn.
No sub-rules.