Is Elemental Mastery legal in Standard, Modern, and Commander?

Elemental Mastery is legal in: Modern, Legacy, Vintage, Commander.

What type of card is Elemental Mastery?

Elemental Mastery is an Enchantment — Aura. Its oracle text reads: "Enchant creature Enchanted creature has "{T}: Create X 1/1 red Elemental creature tokens with haste, where X is this creature's power. Exile them at the beginning of the next end step.""

Elemental Mastery

Enchantment — Aura

Enchant creature

Enchanted creature has ": Create X 1/1 red Elemental creature tokens with haste, where X is this creature's power. Exile them at the beginning of the next end step."