Oreyn only has one duty for you this go around, but it's a good one. A team of fighters (including Viranus Donton) was dispatched to Forgotten Mine to clear out a Troll infestation and hasn't been heard from in days. Find out what happened and report back.
Trolls of Forsaken Mine
Forsaken Mine is just south of Leyawiin on the west bank of the Niben. It may already be on your map if you've been exploring and/or collecting Nirnroots. Otherwise travel to the stables outside of Leyawiin's northwestern gate and just hoof it around the city walls.
It should be pretty obvious from the time that you enter that something has definitely gone wrong; bodies all of the way down, including one dead Blackwood Company fighter. The Blackwood Company armor is worth over 1000 gold for a full suit, but it's heavy armor. If you want it, collect it on the way out. The dead Fighters Guild members have standard armor; nothing special. Interestingly, there are no weapons to be found on or near any of the bodies. Hmmmm. Aside from that, you'll find one Troll and a half-dozen or so Rats and Mud Crabs to keep you occupied on the first level. There are also a half-dozen or so chests which might have some decent goodies.
The second level isn't quite so simple. Eight Trolls and the usual Rats and Mud Crabs (but a good selection of Sacks and Chests). The Trolls are not scattered, but are clumped in twos and threes. Melee types will want to use narrow tunnels to keep them from ganging up on you. Snipers will have a pretty easy go of it. When you get to the bottom you'll find the bodies of Viranus Donton and Eduard Hodge. Donton has a journal that will give you the story as well as some interesting insights from his viewpoint (he thought that he was shepherding you on that trip to Nonwyll, for example). It seems that he and his company were doing a decent job of clearing out the Trolls when the Blackwood Companys showed up and started killing anything that moved (and maybe a few things that didn't). He was wounded, but he and Hodge managed to escape farther into the caves where the Trolls eventually got them.
You'll need to make sure that you get the Journal entry about finding his body (the trigger is sometimes difficult to hit) and, of course, make sure that all of the Trolls are history. That should have happened by this point, but there might be one in the tunnel near Hodge's body. From here you can either hoof it back the way that you came or follow the tunnel near Hodge's body for a shortcut back near the entrance of the second section. Since you'll be able to fast-travel back to Chorrol, you might want to collect that Blackwood Company armor now.
Oreyn takes the news pretty hard, but says that the mission was his responsibility and he'll deliver the news to the Guildmaster. "You still have a career ahead of you." Oreyn, apparently, does not. If you stand outside the guildhall after completing this mission, Oreyn will leave. He won't have any new conversation topics for you until you complete Azzan's and gro-Khash's next set of contracts, but he goes home and more or less stays there.