Is Druid of Horns legal in Standard, Modern, and Commander?

Druid of Horns is legal in: Modern, Pioneer, Legacy, Vintage, Commander, Historic.

Druid of Horns

Q: What type of card is Druid of Horns?

Druid of Horns is a Creature — Human Druid. Its oracle text reads: "Whenever you cast an Aura spell that targets this creature, create a 3/3 green Beast creature token. *No welcome for those who trespass. Only fang and horn and claw.* Power/Toughness: 2/3"