Is Terisian Mindbreaker legal in Standard, Modern, and Commander?

Terisian Mindbreaker is legal in: Modern, Pioneer, Legacy, Vintage, Commander, Historic.

What type of card is Terisian Mindbreaker?

Terisian Mindbreaker is an Artifact Creature — Juggernaut. Its oracle text reads: "Whenever this creature attacks, defending player mills half their library, rounded up. Unearth {1}{U}{U}{U} ({1}{U}{U}{U}: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next end step or if it would leave the battlefield. Unearth only as a sorcery.)"

Terisian Mindbreaker

Artifact Creature — Juggernaut

Whenever this creature attacks, defending player mills half their library, rounded up.

Unearth (: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next end step or if it would leave the battlefield. Unearth only as a sorcery.)