Spell mastery

Spell mastery is an ability word that gives a card different or additional characteristics if its controller has 2 or more instant or sorcery cards in their graveyard.

Description
Introduced in Magic Origins, the mechanic was featured on a vertical cycle of instants and sorceries in each color, plus on another common in black and blue.

Spell mastery is written as "Spell mastery — If there are two or more instant and/or sorcery cards in your graveyard, static ability, self-replacement, activated ability, and/or triggered ability."

Spell mastery was received well enough to return one day. Ghitu Lavarunner is the first permanent to use the Spell Mastery text, though without the ability word.

Rulings

 * 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.