Is Captivating Unicorn legal in Standard, Modern, and Commander?

Captivating Unicorn is legal in: Modern, Pioneer, Legacy, Vintage, Commander, Pauper, Historic.

Captivating Unicorn

Q: What type of card is Captivating Unicorn?

Captivating Unicorn is a Creature — Unicorn. Its oracle text reads: "Constellation — Whenever an enchantment you control enters, tap target creature an opponent controls. *"Gazing at the unicorn, I felt closer to the majesty of Nyx than I ever had before." —Oineus, traveling merchant* Power/Toughness: 4/4"