Gothic/Banishment from the Old Camp

After you have given the remaining Focus Stones to Saturas, and spoken to him about what they need to do next, Saturas will mention needing the original twelve mages (now split into six Mages of Fire and six Mages of Water). He'll tell you to go to find some way to contact Corristo, leader of the Mages of Fire, and attempt to appeal the New Camp's proposition. If you go down to Cronos, by this point, you can begin the equally ill-fated subquest where you seek the aid of the Magicians of Fire.

When you head to the Old Camp to deliver the message to the Mages of the Circle of Fire you'll see a strange sight: both gates are shut and heavily guarded. If you approach they'll say you can't come in, and, if you were a member of the Old Camp (regardless of whether you were a Guard or a Magician of Fire) they denounce you as a traitor and chase after you.

It isn't too difficult to outrun them. Go around to the rear gate until you see Diego. He explains the situation: the Old Mine collapsed when water got in. Gomez, desperate to maintain the constant supply of ore to the outside world that is crucial to his easygoing life, decided to launch an attack on the Free Mine and seized it, killing everyone there. When the Magicians of Fire opposed this plan they were executed.

Diego wants you to track down three others to have what he calls "the meeting", which takes place in an undisclosed location. This quest is optional, so it doesn't matter if you can't find all three.

All you can do is head back to the Magicians of Water and tell them the bad news. They'll let you join their camp (if you were a Guard, join the Mercenaries. If you were a Magician of Fire, join the Magicians of Water). With no other choice available, Saturas will send you to find Xardas the Necromancer.

Note: if you use a scroll to transform into a Meatbug, you can crawl under the closed gate of the Old Camp. You may need to dispatch that gate's guard to avoid them attacking you. As a Meatbug, you can wander around the perimeter areas of the Old Camp safely and take note that all outsiders in the camp were killed. They even killed Kirgo! If you transform into a human again, guards will begin attacking you. Meanwhile, even as a Meatbug, a creature which no other creature in the game naturally attacks, it's not possible to pass the gate into the castle - Thorus and his guards will attack.

Starting from different places above the Old Camp, the path and plateaus leading up to the look-out fort ruins, and the ruins of the look-out fort itself, I've had varying chances of getting onto that tarp above the back area of the Old Camp, using a Transform into Bloodfly scroll. Bloodflies are useful since they travel forward quickly and, because they fly, have a little lessened fall damage.