Spells you cast cost less to cast if they were originally printed in the following expansions or associated commander decks, depending on who won the Unknown event on February 18th, 2023:
Mirran Victory — Mirrodin, Darksteel, Fifth Dawn, and Scars of Mirrodin.
Phyrexian Victory — Mirrodin Besieged, New Phyrexia, All Will be One, and March of the Machine.