The token creatures all enter the battlefield at the same time.

A token that enters the battlefield as a copy of a face-down creature is a face-up colorless 2/2 creature with no name, abilities, or creature types.

Each token copies exactly what was printed on the original creature and nothing else (unless that permanent is copying something else or is a token; see below). It doesn't copy whether that creature is tapped or untapped, whether it has any counters on it or Auras and Equipment attached to it, or any non-copy effects that have changed its power, toughness, types, color, and so on.

If the copied creature has in its mana cost, X is considered to be zero.

If the copied creature is copying something else, then the token enters the battlefield as whatever that creature copied.

If the copied creature is a token, the token created by Clone Legion copies the original characteristics of that token as stated by the effect that put the token onto the battlefield.

Any enters-the-battlefield abilities of the copied creature will trigger when the token enters the battlefield. Any "as [this permanent] enters the battlefield" or "[this permanent] enters the battlefield with" abilities of the copied creature will also work.

Remember that if you control more than one legendary permanent with the same name, you'll choose one to remain on the battlefield and put the rest into their owners' graveyards.