Diego sets you a test for the Old Camp: fetch a supply list from Ian, deep in the Old Mine. The catch is that Ian will not just hand it over, so you need the right words from Diego before you go, plus a map from 
Graham to find the way. Ask Diego about the hungry crawlers first, or you will be making the trip twice.
The journey matters more than the fights here, and one early line of dialogue saves you a long backtrack.
- Healing potions.
- Food.
- A decent weapon.
- A torch if you travel at night.
Before you leave the Old Camp, ask Diego about the crawlers looking hungry. Skip it and you may have to walk all the way back from the mine to get it.
Start with Diego in the Old Camp. Make sure you ask him about the line 'the crawlers look mighty hungry,' since that is what later convinces Ian to give up the list. After that, hear him out about Graham, who has the map you need.
Go to the north gate of the Old Camp, the wooden one, and turn left to a group of people with Graham among them. Talk to him.
Rather than pay for the map, take the forceful line, 'I'm not paying, give me the map or else,' and Graham hands it over. Open it and look for the X that marks where you are headed.
If it is getting dark, sleep at Mud's shack until morning to make the trip out safer.
Head out through the wooden north gate and cross the bridge. On the far side, go left. The main path has the tougher enemies, so the lower route around toward the mines is the gentler way, even if a few enemies still turn up.
At the Old Mine, head inside and follow the tracks around to the left. Carry on to the bridge, cross it into the small village section built into the mine, then go right and start working your way down through the caves.
Keep descending until you reach a damp, blue-lit open area, then take the platforms and ramps down to the lower village. At the bottom you pass Orbis by a ladder. Turn around toward the lit area, and Ian is at the table. Speak to him.
Ask Ian for the supply list. He balks at first, and this is where the earlier talk with Diego pays off. Choose the line about the crawlers looking mighty hungry, Ian realizes Diego sent you, and he hands over the supply list.
Leave the mine and head back to the Old Camp, watching for enemies on the way. Give the supply list to Diego to finish the quest.
If Diego is not around when you get back, sleep and check again later, and he should turn up.