Is Team Avatar legal in Standard, Modern, and Commander?

Team Avatar is legal in: Standard, Modern, Pioneer, Legacy, Vintage, Commander, Historic.

Team Avatar

Q: What type of card is Team Avatar?

Team Avatar is an Enchantment. Its oracle text reads: "Whenever a creature you control attacks alone, it gets +X/+X until end of turn, where X is the number of creatures you control. {2}{W}, Discard this card: It deals damage equal to the number of creatures you control to target creature."