Orbital Skull
The Orbital Skull is one of the new skulls that give you an achievement, and it gives 25 gamer points. It is unknown weather if it is even a skull but most likely it is because it gives you an achievement that looks like the ones you get when you get a gold skull in Halo 3. It is unknown where it is found because it is not out yet. It will come out with the mythic upgrade.
Please add more if you know more about this skull!