After completing Azzan's two contracts and gro-Khash's contract, you'll be shipped off to Chorrol to perform guild duties. Duties are quests that benefit the guild rather than the client. Your initial contact will be with the Guildmaster, Vilena Donton (don't try anything funny - she's 40 levels above you and "essential"). But over the course of the story you're going to get more information about her than you will information from her. All she does is send you downstairs to see Modryn Oreyn.
Oreyn sends you off to Skingrad to see a new guild member named Maglir (an "eight-pint" warrior according to other guild members), who seems to have defaulted on a contract. This reflects badly on the guild, so you're to find out what the problem is and fix it. Maglir hangs out at the West Weald Inn. You may have already spoken to him if you've needed to find Sinderion for the "Seeking Your Roots" quest or otherwise dropped into the West Weald Inn.
When you talk to Maglir, he doesn't make any bones about defaulting. As far as he's concerned, having a family to think about and all, he's not paid nearly enough for the risks associated with this particular contract. The contract is to recover the journal of Brenus Astis from Fallen Rock Cave and he says that you're welcome to it.
Having found out that Maglir has, indeed, defaulted on the contract, you might be tempted to hightail it back to Chorrol and report "mission completed" since that's what you were sent to do. I'll save you the trouble -- don't bother. Oreyn will just send you back to Fallen Rock Cave to recover the journal and complete the contract.
Fallen Rock Cave is just a bit west of Bleak Flats Cave, where you had to go for your recommendation letter from the Skingrad Mages Guild. If you don't have that on your map, you'll just have to head northwest from Skingrad's west gate and follow your compass until you get there. You'll run into Rats, Mud Crabs, and some leveled undead. Assuming you're not leveled into the teens, you probably won't need anything special to hit the undead, but there will probably be at least a Ghost or Wraith or two where you'll need either an enchanted weapon or at least something Silver or better to damage it, so plan and equip accordingly.
There's nothing complicated about Fallen Rock Cave aside from a couple of falling rock zones where you can get bonked if you're not careful. It only has one level and the journal is (you guessed it) almost all of the way to the back. It's out in the open on a rock shelf beside a chest. It seems that Benus Astis was a bit of a field researcher with an interest in the fauna of the area, so you'll find some notes (incomplete) on Rats, Trolls, Minotaurs and something called a "land dreugh". It's somewhat interesting reading, but there are no skill boosts attached to it.
Once you have the journal, you can go talk to Maglir again if you want. You're offered two options: claim the credit for fulfilling the contract or give him the credit for it (he says "whatever" to either choice). If you claim the credit when you talk to Oreyn, you'll get the point of Fame for fulfilling the contract, but it will make your life a little more difficult later. If you give Maglir the credit for it, you won't get the Fame, but it will make Maglir more willing to talk to you later. You get the gold either way. Oreyn isn't impressed if you give Maglir credit for completing the job, by the way, and you'll catch rumors here and there that the guild covered up a flubbed contract. You'll also note that the "Duties" thread is still lit. Yep, Oreyn has something else for you to do.
Drunk and Disorderly
Off to Leyawiin you go to find out why three guild members are causing trouble. The guild members, (Dubock gro-Shagk, Rellian and Vantus Prelius) are holed up at the Five Claws Lodge. The place is a mess and it sounds like a big argument if you stand a listen to them for a while (with the innkepper pitching in occasionally, too). But all they do is hurl insults and order more drinks. They aren't just drunk. They're angry at losing contracts to some outfit called the "Blackwood Company" that has recently opened up shop in town. Prelius suggests that if you'd like them to leave, find some work for them.
Finding work isn't that big of a deal, frankly. Anyone in Leyawiin, even those who dislike you a little, will point you to Margarte. Margarte wanders around a lot, so you'll just need to follow your compass to find her. Don't be surprised to find her a bit west of the city since her hobby is alchemy and she collects ingredients. In fact, she needs Minotaur Horns and Ogres' Teeth for some experiments she's doing and she doesn't trust the Blackwood Company to deliver. She doesn't really trust you, either, but if you can bring her five portions of Ectoplasm she'll give the Fighters Guild an exclusive contract to supply her with the teeth and horns.
If you're a low-level character, finding Ectoplasm might be problematic. If you want to take the easy way out, go buy Ectoplasm from an alchemist. You can probably find some at "All Things Alchemical" in Skingrad or at the "Golden Carafe" or "Main Ingredient" in the Imperial City.
If you don't want to do it that way, Ectoplasm is what Ghosts and Wraiths leave behind and those aren't random creatures at lower levels. So you'll need some that are pre-placed if you want to be 100% certain of getting it. I can think of three places that are immediately accessible: Benerus Manor in Anvil (you'll need to have 5,000 gold to purchase the manor, but you'll get infinitely spawning ghosts and a nifty house out of the deal), the ship that's tied up at the Anvil docks has a quest ("The Ghost Ship of Anvil") that will require you to kill about a half-dozen ghosts or wraiths, and you can find ghosts in any chapel undercroft (usually a couple or three). You probably picked up a couple of portions in the "Unfinished Business" quest that you just completed. Margarte doesn't care where the Ectoplasm comes from; just that you bring her five portions of it.
However you get it, deliver it to Margarte. The horns and teeth contract is sealed (meaning you can sell them to her, too -- 500 golds for each set of five that you bring her), and you can go tell your guildmates that you found work for them go report "mission completed" to Oreyn. Your guildmates are happy, the innkeeper is happy, the guild is happy, you're happy (and get a promotion to Swordsman out of the deal). Everyone wins (except the ogres and minotaurs).