Mythic
From Halopedia, the Halo wiki
Mythic is a "fan-made" difficulty. In order to play it, set the game to Legendary and turn on all the Skulls. Mythic is possible in Halo 2, Halo 3, Halo 3: ODST, Halo: Reach and Halo: Combat Evolved Anniversary. Another short way of saying it would be "LASO", which means Legendary with All Skulls On. Although it can be beaten, the game will still say "Legendary" since Mythic does not exist in the game's code. For the same reason, the difficulty does not have an icon like the official ones.
