I loaded a saved game, and transported from Aman'lu to Western End of Arinth's Ravine. Then to east from the teleporter and in the second climb up (before the cave) I found a couple of Fettershins and Vai'kesh Zealots.
In the middle of the fight, a creature appeared from the north corner and headed to the trees in the south corner. It looked like a fat short gnome. I tried to kill it but it ran away. It was fast (I wasn't smart enough to take a screenshot), and it was LVL100 and had something like "<<<" for a name. I believe it didn't attack me, but I also believe it took something from the ground.
It is named ???. You can learn more about it [url="http://www.gamebanshee.com/dungeonsiegeii/walkthrough/themysteriousquest.php"]here[/url].
SWC
Sir Edmund:"Should you obey the lord who asks you to put a village of innocents to the torch? Is that chivalrous? Is it noble?" Me:"It's a great way to get promoted, I know that much."
