格子窓の図書館

If you cast your first spell with {X} in its mana cost during a turn before Lattice Library is on the battlefield (including Lattice Library itself), casting another spell with {X} in its mana cost later in the turn won't cause its last ability to trigger.

Lattice Library's last ability resolves before the spell that caused it to trigger. It resolves even if that spell is countered or otherwise leaves the stack.