Does a token that becomes a copy of a legendary creature trigger the legend rule?

When a token becomes a copy of a legendary permanent, it gains every copiable characteristic of that permanent, including the legendary supertype. This is established by CR 706.2, which defines what characteristics are copied: name, mana cost, color indicator, card type, subtype, supertype, rules text, abilities, power, and toughness.

The legend rule (CR 704.5j) is a state-based action that checks whether a player controls two or more legendary permanents with the same name. State-based actions are checked continuously, so the moment the token becomes a legendary copy, the game immediately checks whether the legend rule is violated.

If the copied creature's controller already controls another legendary permanent with the same name — such as the original creature the token is copying — that player must choose one to keep and put the rest into their graveyard. This applies equally to permanents and tokens; tokens are permanents on the battlefield (CR 110.1).

Concrete example: You control a legendary creature named Adrix and Nev, Twincasters. An effect creates a token that becomes a copy of it. Now you control two legendary permanents both named Adrix and Nev, Twincasters. State-based actions trigger, and you must immediately put one of them into the graveyard (you choose which to keep).

Note that if the token is not already named the same as any other legendary permanent you control, no legend rule violation occurs — the rule only triggers when two or more legends share the exact same name under your control (CR 704.5j).