Gideon's Phalanx — ruling 1

If the spell mastery ability applies, the four Knight tokens will also gain indestructible until end of turn.

Gideon's Phalanx — ruling 2

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.

Gideon's Phalanx : règles, fonctionnement et interactions (MTG)

Gideon's Phalanx 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

Create four 2/2 white Knight creature tokens with vigilance. Spell mastery — If there are two or more instant and/or sorcery cards in your graveyard, creatures you control gain indestructible until end of turn.

How it works : Gideon's Phalanx

Original English text — Wizards of the Coast / Scryfall

#1June 22, 2015· Wizards of the Coast
If the spell mastery ability applies, the four Knight tokens will also gain indestructible until end of turn.
Card named in this ruling
Knight
#2June 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.