This instructable will help you get the HALO 3 Mythic Map Pack skulls. I have not got the mythic map pack but my friend does and I helped him get the three achievements. My first instructable.
Step 1: Assembly Skull
The middle part of the map is the big tower, Right? If so their are pipes Joined to the sides. The Skull is in One of those. *note: not in the Pipe, Next to the top of one
Step 2: Sandbox Skull
This place is Huge? Basement, Sky and The Ground Floor Download the map from this site, Please don't worry this is an official Bungie Web site.
Step 3: Orbital Skull
This skull is on a ledge in an open room not much in there but the skull is all you gotta do to find this skull is look on ledges in high places (actually its not really a ledge it looks more like a giant CD rack)
Step 4: Thank You for Looking
If you Managed to Ge the Skulls using my walkthrough You are good Because im not good at describing things...