Is Epistolary Librarian legal in Standard, Modern, and Commander?

Epistolary Librarian is legal in: Legacy, Vintage, Commander.

Epistolary Librarian

Q: What type of card is Epistolary Librarian?

Epistolary Librarian is a Creature — Astartes Wizard. Its oracle text reads: "Veil of Time — Whenever this creature attacks, you may cast a spell with mana value X or less from your hand without paying its mana cost, where X is the number of attacking creatures."

Creature — Astartes Wizard

Veil of Time — Whenever this creature attacks, you may cast a spell with mana value X or less from your hand without paying its mana cost, where X is the number of attacking creatures.

Set Warhammer 40,000 Commander

Rarity Rare

Mana Value 4

Artist Games Workshop

Collector # 118

Scryfall Gatherer