The Champion Mask is a mask that is a direct upgrade to the. Warrior Mask If you have it equipped when you spawn, you will spawn with 250 health and a Steel Warhammer. To obtain the Champion Mask, you must have survived in Hardcore mode for a total of 150 seasons. This is very hard to do (although not as hard in comparison to masks like the Crown), and in return is the most powerful mask for the fighters in a server.
In appearance, it has a wide mouth with Hexagon-like eyes. It has completely straight red "ears" and red antlers. This is probably just a more menacing take on the Warrior Mask.