At the beginning of your upkeep, detain target creature an opponent controls. (Until your next turn, that creature can't attack or block and its activated abilities can't be activated.)
If a noncreature permanent is detained and later turns into a creature, it won’t be able to attack or block.
If a creature is already attacking or blocking when it’s detained, it won’t be removed from combat. It will continue to attack or block.
Activated abilities include a colon and are written in the form “[cost]: [effect].” No one can activate any activated abilities, including mana abilities, of a detained permanent.