I just came from a boss battle with my friend Tasha Rosesword she used an Myth King Arthur card on the boss Elana Darksun at 2000 health and the boss recieved 0 damage, I am returner to the game but, are the damage different from what they use to be?
It is for that spell, yes. Myth's King Artorious spell was changed so that it instead of doing damage every turn for 3 turns, it instead will do all of its damage at once. You just need to wait 3 turns for it to take effect.