Legendary creatures don't untap during their controllers' untap steps.When Arena of the Ancients enters the battlefield, tap all legendary creatures.
Regler omkring kortet.205.4 Supertypes205.4a A card can also have one or more supertypes. These are printed directly before its card types. The supertypes are basic, legendary, ongoing, snow, and world.205.4b An object’s supertype is independent of its card type and subtype, even though some supertypes are closely identified with specific card types. Changing an object’s card types or subtypes won’t change its supertypes. Changing an object’s supertypes won’t change its card types or subtypes. When an object gains or loses a supertype, it retains any other supertypes it had.205.4c Any land with the supertype “basic” is a basic land. Any land that doesn’t have this supertype is a nonbasic land, even if it has a basic land type.205.4d Any permanent with the supertype “legendary” is subject to the state-based action for legendary permanents, also called the “legend rule” (see rule 704.5k).205.4e Any permanent with the supertype “world” is subject to the state-based action for world permanents, also called the “world rule” (see rule 704.5m).205.4f Any permanent with the supertype “snow” is a snow permanent. Any permanent that doesn’t have this supertype is a nonsnow permanent, regardless of its name.205.4g Any scheme card with the supertype “ongoing” is exempt from the state-based action for schemes (see rule 704.5w).