Enter Old Seb, go through the doors till you come close to the water for the first time. Turn left, cross the broken bridge, to a pyramid like structure with a locked door and a moat of water in front. There are a number of frogloks of the living variety in front guarding it. It would be a good idea to kill those frogloks closest to the door even if you invised successfully that far. I read else where that it takes a rogue with 200 lock pick to open the locked door. Lacking a rogue, shrink, and shadow step across the door. There are boots usable by certain classes with cliky shadow step on them. I beleive there are potions with this effect also. Some classes have shadowstep or similar available at low levels. You may not cross the door the first time you shadow step, but eventually you will. It took me ten tries once yesterday, one try today. Probably you will land in the hallway, but you could land a little further in where there is a room with three or four mobs with pets. Thia is a part of the zone with undead ghoul guktans, their skeleton pets, and skeletons almost exclusively with an occasionally an iksar spectre. Wind around a bit till you find a room which has a walk way down the middle and bleacher like steps on both sides. There is a golem at the top center of the bleacher on both sides. Behind one of the four doors at the top of the bleachers is a smallish room which has a place holder called 'skeletal baron'. When I was trying to find Baron Yosig, this spot always popped 'skeletal baron', and this was the only mob up with that name on several clears of the skeletons and ghouls. The PH stands right at the foot of an apparent coffin. Kill 'skeletal baron' repeatedly till Baron Yosig pops. I had about ten kills to get Baron Yosig to pop once, and the pop time was about ? 20 minutes. He dropped the Journeyman's Walking Stick and a sunshard pebble.
Avoid AE spells in this area. I fired off one, and found myself dealing with shrooms on the level just above or below the undead, having been summoned by an angry shroom. I had to zone out and return due to loosing my way in the tunnels.