Is Briarblade Adept legal in Standard, Modern, and Commander?

Briarblade Adept is legal in: Legacy, Vintage, Commander, Pauper.

What type of card is Briarblade Adept?

Briarblade Adept is a Creature — Elf Assassin. Its oracle text reads: "Whenever this creature attacks, target creature an opponent controls gets -1/-1 until end of turn. Encore {3}{B} ({3}{B}, Exile this card from your graveyard: For each opponent, create a token copy that attacks that opponent this turn if able. They gain haste. Sacrifice them at the beginning of the next end step. Activate only as a sorcery.)"

Briarblade Adept

Creature — Elf Assassin

Whenever this creature attacks, target creature an opponent controls gets -1/-1 until end of turn.

Encore (, Exile this card from your graveyard: For each opponent, create a token copy that attacks that opponent this turn if able. They gain haste. Sacrifice them at the beginning of the next end step. Activate only as a sorcery.)