It is represented by a blue circle with a skull in the foreground. The skull has a swirl on its forehead. All enemies are given double their usual health, and the skull can be found on the last level in Halo 3. Also, Mythic is considered a new difficulty level, above Legendary, for an extra challenge.
Stay on the right wall until you find a cave. Keep going through and you will find it. It is considered one of the easier skulls to find, just barely being off of the main path of its level, and at the very beginning.
- The emblem on the skull is used on the skull in the advertisement of the Mythic map pack. This is due to the names of the map packs being the difficulty levels (Heroic, Legendary, etc.). With the Mythic Skull on, while playing on Legendary, it is considered to be the hardest difficulty in the entire game.