"I've sworn to protect the people from the horrors that would destroy them—even if those horrors are the angels themselves."

Thalia, Guardian of Thraben

First strike
Noncreature spells cost {1} more to cast.

No stranger to monstrous foes, Thalia marshaled surviving cathars, townspeople, and even ghoulcallers into an unbreakable fighting force.

Multiverse Legends

"Thraben is our home and I will not see it fall to this unhallowed horde."

"Thraben belongs to the living. I will not rest until it is cleansed."

Innistrad: Double Feature

Thalia's ability affects each spell that's not a creature spell, including your own.

To determine the total cost of a spell, start with the mana cost or alternative cost you're paying, add any cost increases, then apply any cost reductions. The mana value of the spell remains unchanged, no matter what the total cost to cast it was.