Is Rathi Assassin legal in Standard, Modern, and Commander?

Rathi Assassin is legal in: Legacy, Vintage, Commander.

What type of card is Rathi Assassin?

Rathi Assassin is a Creature — Phyrexian Zombie Mercenary Assassin. Its oracle text reads: "{1}{B}{B}, {T}: Destroy target tapped nonblack creature. {3}, {T}: Search your library for a Mercenary permanent card with mana value 3 or less, put it onto the battlefield, then shuffle. Power/Toughness: 2/2"