There are 4 ways to get back to Mt Gigas one of which is impossible to use unless you came from Mt. Gigas that way.1. (easiest) From the entrance to MB proceed west northwest through the Swamp to Trynton, Trynton to Trynton-Arnika Rd, T-A Road to Arnika Road, Arnika Road to NW Wilderness,
Nw Wilderness to UBC. This route is the easiest because you are moving through mostly civilized areas where you can resupply easily.
2. (harder) From the entrance to MB proceed north through the Swamp cross the bridge at the center of the Swamp then priceed north west across the Swamp to the Mine Tunnels. Mine Tunnels to Lower Martins Bluff, LMB to MB, MB to LMB, Half way through this part of LMB you can access the T'rang transporter. This transporter once fixed by using the red and yellow wires you found near the T'rang arm (you did find the t'rang arm
) can take you to 1 of 4 places Arnika-Trynton Rd. Mine Tunnels, Rapax Rift, and NW Wilderness. This route is harder because the monster levels are higher and in the Mine Tunnels area are attacking frequently
3. (hardest) From MB go east through the Swamp to the entrance of the SE Wilderness, SE Wilderness to Mountain Wilderness, Mt. Wilderness to NW Wilderness, NW Wilderness to UBC. This route is the hardest because you will face the toughest monsters outside of Ascension Peak.
4. (impossible) Unless you came to Marten's Bluff from Mt. Gigas by this route you will be unable to go very far into Mt Gigas because of a large steel door that can only be unlocked fro the uther side. From MB go north through the Swamp cross the bridge continue through the Swamp to Bayjin, Bayjin to Bayjin Shallows, BS to Umpani Underwater caves, UUC to Mt Gigas. The monsters here are as bad as #3 and at the end of your trip to be faced with a locked door that you can't open from that side well...
Hope that this info helps you as you wander around the wonderful world of Dominus. Good luck and good hunting.