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

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

Nyxborn Unicorn

Q: What type of card is Nyxborn Unicorn?

Nyxborn Unicorn is an Enchantment Creature — Unicorn. Its oracle text reads: "Bestow {3}{W} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached.) Mentor (Whenever this creature attacks, put a +1/+1 counter on target attacking creature with lesser power.) Enchanted creature gets +2/+2 and has mentor."