Is Arthur, Marigold Knight legal in Standard, Modern, and Commander?

Arthur, Marigold Knight is legal in: Legacy, Vintage, Commander.

Arthur, Marigold Knight

Q: What type of card is Arthur, Marigold Knight?

Arthur, Marigold Knight is a Legendary Creature — Mouse Knight. Its oracle text reads: "Haste Whenever Arthur and at least one other creature attack, look at the top six cards of your library. You may put a creature card from among them onto the battlefield tapped and attacking. Put the rest on the bottom of your library in a random order. Return that creature to its owner's hand at end of combat."

Legendary Creature — Mouse Knight

Haste

Whenever Arthur and at least one other creature attack, look at the top six cards of your library. You may put a creature card from among them onto the battlefield tapped and attacking. Put the rest on the bottom of your library in a random order. Return that creature to its owner's hand at end of combat.

Set Bloomburrow Commander

Rarity Mythic Rare

Mana Value 5

Artist Steven Belledin

Collector # 5

Scryfall Gatherer