Cheapest priced copy (Magic Origins): $0.35 at Card Kingdom, near mint, their price list as of .
Kytheon's Tactics 
Sorcery · Common · Magic Origins · #25
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.)
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Magic Origins | 25 | Common | $0.35 | $0.49 |
One ruling from Wizards of the Coast
- 22 June 2015Check 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.