MyriadMyriad is a triggered ability that may also create a delayed triggered ability. “Myriad” means “Whenever this creature attacks, for each opponent other than defending player, you may create a token that’s a copy of this creature that’s tapped and attacking that player or a planeswalker they control. If one or more tokens are created this way, exile the tokens at end of combat.”
If a creature has multiple instances of myriad, each triggers separately. (CR 702.116)
The "legend rule" doesn't apply to creature tokens you control.
Triggered abilities you control can't cause you to
sacrificeTo sacrifice a permanent, its controller moves it from the battlefield directly to its owner’s graveyard. A player can’t sacrifice something that isn’t a permanent, or something that’s a permanent they don’t control. Sacrificing a permanent doesn’t destroy it, so regeneration or other effects that replace destruction can’t affect this action. (CR 701.21) or
exileTo exile an object, move it to the exile zone from wherever it is. See rule 406, “Exile.” (CR 701.13) creature tokens you control.