Saturas sends you to the Monastery Ruins for a Focus Stone, where 
Gorn meets you and leads you below. Getting inside means turning into a 
meatbug to slip through a crack in the wall, then opening the gate for Gorn from the other side. Past that it is a long crawl through 
Snapper caves, a Shadowbeast, and a Juvenile 
Troll on the way out.
There is a lot of fighting in here and a couple of spots that can catch you out, so come stocked and save often.
- Healing potions.
- Food or backup healing.
- A good weapon.
- Strong armor if you have it.
Expect a string of Snappers, a Shadowbeast partway through, and a Juvenile Troll near the end.
Travel to the Monastery Ruins, at the top point of the star-shaped marker. Gorn is waiting. Talk to him, then follow him down into the caves beneath the ruins.
Gorn leads you into a cave and a short scene plays. Loot everything you can find here, the potions, goblets, and odds and ends, but above all the chest at the back. Inside is the 
Transform into Meatbug scroll, and you do not want to leave without it.
Head back up the mud path with Gorn toward the main gate, and set the scroll in your quick slot. At the gate, go to the left, where there is a small hole in the wall with meatbugs around it. Cast the scroll to become a meatbug and crawl through the gap.
Keep going as far as the gap allows, then go up, right, and out into the courtyard. The Snappers ignore you while you are a meatbug, so cross the courtyard freely.
Make for the right side of the courtyard, where the gate stands with Gorn on the far side. Turn back to your normal form, clear the Snappers in the courtyard, then use the cog mechanism on the wall to the right of the gate to open it. Speak to Gorn, who stays outside, so you press on alone from here.
From the courtyard, head to the back-right corner to an entryway. There is loot inside if you want it, and you pass back through later anyway. Go slightly right, through the gap in the wall, and follow the route carefully without falling. Climb the rocks into the room above.
Inside, climb onto the small rock section, step onto the wooden platform, and turn around. Go out the door, right, through the next doorway, and right again, which brings you toward the cave at the back.
The cave is crawling with Snappers, so save often, since nearly every opening hides another one. The first room has a side room on the right with loot if you want it. To stay on the main route, take the left path downward and keep fighting through until you reach a large open room.
Clear the Snappers in the open room, then head left until you see mushrooms on the ground by a drop-down point.
Save before you drop. A Shadowbeast waits below and it can punish a careless landing.
Drop in and fight the Shadowbeast. Loot it once it is dead, the drops are useful later and sell well, then head to the back-left and through the passage in the cave wall, picking up any herbs on the way.
Follow the passage to the Focus Stone and pick it up. Turn around: directly behind where it sat, a corridor leads back into the ruins. Take it, go up the stairs and up again, loot the rooms, and use the small handle beside the door. That opens a shortcut back to the earlier room by the courtyard, closing the loop.
As you leave, there is a loud crash. Do not stop, just keep running forward until you reach Gorn. Tell him you have the Focus Stone.
A Juvenile Troll turns up around then. The simple way is to run and let Gorn do most of the work. Once he has worn it down and it bolts, chase it, finish it off, and loot it for a big chunk of experience.
Speak to Gorn again if there is more to say, then leave the Monastery Ruins. Travel to the New Camp, find Saturas, and hand over the Focus Stone to finish the quest.