Union Arena - Jujutsu Kaisen | My Boxes Are Better Than Yours | Episode One

[@Raimundo627]

Please note that Dagon's when sidelined ability only occurs when it is sidelined from the field by combat or effects

[@DJRUnion]

Thank you for pointing this out. We went back to double-check the rulings to make sure we get more things right in the future and found on the website that Dagon's "when sidelined" ability does, in fact, trigger when discarded with Mahito's ability