Is Klauth, Unrivaled Ancient legal in Standard, Modern, and Commander?

Klauth, Unrivaled Ancient is legal in: Legacy, Vintage, Commander.

Klauth, Unrivaled Ancient

Q: What type of card is Klauth, Unrivaled Ancient?

Klauth, Unrivaled Ancient is a Legendary Creature — Dragon. Its oracle text reads: "Flying, haste Whenever Klauth attacks, add X mana in any combination of colors, where X is the total power of attacking creatures. Spend this mana only to cast spells. Until end of turn, you don't lose this mana as steps and phases end."

Legendary Creature — Dragon

Flying, haste

Whenever Klauth attacks, add X mana in any combination of colors, where X is the total power of attacking creatures. Spend this mana only to cast spells. Until end of turn, you don't lose this mana as steps and phases end.

Set Forgotten Realms Commander

Rarity Mythic Rare

Mana Value 7

Artist Andrew Mar

Collector # 50

Scryfall Gatherer