Veil of Time — Whenever Epistolary Librarian 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.
"Bolters? Chainswords? All fine weapons, however I wield a far more dangerous power."
In Two-Headed giant and other formats where multiple players can attack at the same time, Epistolary Librarian's triggered ability counts all attacking creatures, even those controlled by other players.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.