Oketra's Monument

Each Monument's triggered ability triggers as the creature spell is cast and resolves before that creature spell resolves. The ability will resolve even if that creature spell is countered.

Each Monument has one ability that reduces the cost of creature spells of a certain color, and a triggered ability that triggers whenever you cast any creature spell—not just a creature spell of that color.

To determine the total cost of a creature 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 creature remains unchanged, no matter what the total cost to cast it was.