Kytheon's Tactics — ruling 1

Check to see if there are two or more instant and/or sorcery cards in your graveyard as the spell resolves to determine whether the spell mastery ability applies. The spell itself won’t count because it’s still on the stack as you make this check.

Kytheon's Tactics : règles, fonctionnement et interactions (MTG)

Kytheon's Tactics 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

Creatures you control get +2/+1 until end of turn. Spell mastery — If there are two or more instant and/or sorcery cards in your graveyard, those creatures also gain vigilance until end of turn. (Attacking doesn't cause them to tap.)

How it works : Kytheon's Tactics

Original English text — Wizards of the Coast / Scryfall

#1June 22, 2015· Wizards of the Coast
Check to see if there are two or more instant and/or sorcery cards in your graveyard as the spell resolves to determine whether the spell mastery ability applies. The spell itself won’t count because it’s still on the stack as you make this check.
No other card is named in this ruling.