This quest occurs after you vanquish the Shade Lord in the Temple Ruins, but other than that, I think it is somewhat random. Upon entering the Umar Hills area, a druid spirit will approach you and complain of destruction that is taking place in the forests near the old temple. Once again, the Temple Ruins area.

At the Temple Ruins, you will meet Lord Igen Tombethen, who will only speak to your main character. After speaking with him, you learn that he is looking a lost stash of Mithril that his ancestor, Idras Tombelthen's journal mentioned. At this point you can just demand he leaves and engage in battle, however I would suggest at least traveling to the area guarded by a few skeletons. Dispatch them and then look in one of the rock outcroppings to find a note and a Mithril amulet. Retrieve these and return to speak with Igen.

Here is where a bit of decision-making comes into play. You can tell Igen you have recovered the Amulet and he will give it to you for 1000 gold. You can decline and give it to him for free, or demand 2000 gold. If you try and drive the price up he will only offer 500 gold. You can either give it up, or fight him and his party, thus saving the forest and keeping the loot. Its just a matter of your alignment. Note that the vendor in the Umar Hills offered me 0 gold for it. This may just be the one vendor, or perhaps it is better to take the 1000 gold and run.

Return to your cabin in the Umar Hills and the druid spirit will thank you for saving the forest and you will receive 21,500 experience points. The second time through, I chose to fight for the amulet, so I'm unsure if the experience varies with or without violence.

Some time after you've saved the forest, you will receive word (from a boy named Donovan I believe) that the town in the Umar Hills is under attack by monsters, and they need your help. Go to the Umar Hills and talk to the Mayor. He will tell you that the monsters are located in a cave on the North side of the river, and a child is missing. Go to the cave where you should have gotten the mimics blood the first time you were in the Umar Hills (site 6 on the Umar Hills map). Outside the cave there are a few Orogs and Orcs that will attack you. It's a very easy battle. Go inside the cave and you will find Madulf (the friendly Ogre) with the boy. Speak to Madulf and get your experience for completing the quest.

Again, some time later, the same boy will find you and inform you that the town is threatened again. This time the Umar Witch has shown up and has said that if all of the townspeople don't leave within a few days that they will be killed. Go to the town and talk to the Mayor and he will flesh out the story and tell you that the Witch has set up base in the old Temple Ruins.

Go to the Shade Lord Dungeon (site 2 on the Temple Ruins map). The Druid spirit will be outside the entrance. She will tell you what you already know (the Umar Witch is inside). Upon entering you will be attacked by zombie. Go to your right (room 1 on the Temple Ruins 2 map) and there will be a Demon of some sort to fight (easy). Proceed to room 4 (where the sun gem was). On the way there, zombies and skeletons will attack, and they will continue to respawn. In room 4 you will find an evil Cleric with a Mephit. It turns out she is an impostor and not too tough either. Kill her and proceed outside. Talk to the druid spirit to receive your experience.

I am not sure of the experience point totals for the quests, but I believe they were both ~20,000xp + kills, so they are worth the time.