Epistolary Librarian — ruling 1

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.

Epistolary Librarian : règles, fonctionnement et interactions (MTG)

Epistolary Librarian is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

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.

How it works : Epistolary Librarian

Original English text — Wizards of the Coast / Scryfall

#1October 7, 2022· Wizards of the Coast
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.
No other card is named in this ruling.