I thought I would expand a bit here on the philters used to get to the Overking, so others will know exactly what to expect when using the Shadowstep technique.
I was fortunate enough to obtain the assistance of a level 90 SK, Westa Terrabelle on the Xegony server---thank you Westa! We originally attempted to get to this mob one Saturday afternoon and had no problems getting to the infamous locked door with no way of getting it opened. This was very disappointing and scuttled our attempt that day. I almost thought that was the end of the quest for my cleric but it forced me to research other options, which I found here.
Encouraged, I immediatly began adjusting the faction of my level 60 Bard, a skilled lockpick who could get the SK in without problems. Took him to Nurga and killed the first several rooms again and again, collecting all the salts and skins I could find. In about a week he went from "Scowls" to "Dubious". This allowed him to simply walk down to the royal chambers where I could experiment with the door at leisure with the necessary Philters discussed here.
On an average attempt you will need the following: "Philter of Goulons Impunity"--float, "Philter of the Ant"--shrink and "Philter of Minor Translocation"--shadowstep. There are other incidental Philters such as Major Translocation to gate out, but the three listed above are the most important. I went to the bazaar hoping to buy them but found the supply there sadly lacking. Over time, most vendors find what will sell and what will not and adjust their supply to the most popular. I found readily the shrink and float potions but could never find the shadowstep there.
I have a level 45 Shammy who needed to learn a trade, so I set about learning Alchemy. You can actually get to level 200 just by doing the line of Philters and all the components are readily available in POK. In no time I had full stacks of everything needed to complete the deed loaded on the Bard for my experiments. The only problems he encountered was the energy shields just outside the royal residence which stopped him for a bit, drained some life and then let him go. Now positioned at the door, I made sure his lockpick skills were up to par and the door opened without problem. Incedentally, the mobs beyond the door also conned "Dubious", so one is considered dubious all the way to the royal chambers. This I tested by taking him all the way down for tea and cookies with Himself and the Misses, not to mention Lil Junior.
Back to the door, I had read here that I would need to shrink the bard twice before trying Shadowstep, so I shrunk him twice and then ran him at the closed door so that he could look into the other room and fired off a Shadowstep which propelled him into the next room. I did this 3 more times, each time running at the door and each time it took him instantly into the adjacent room. Confident that I knew what I was doing, I logged the bard at the door where he'd be in position to let Westa into the room on the day of the attempt.
The day we did the Overking I depended on Westa to get the cleric down to the royal residence and instructed her to kill everything from the front door to the locked door, including the roamers. Also set her to killing all rooms nearby while I logged out the cleric to bring in the bard. Since the SK's get Shadowstep, Westa was highly dubious that the spell would work. She's used the spell before and considered it the most worthless spell in the SK spellbook. Getting the bard in, I unlocked the door and told her to 'sanitize the room next door' while I logged the bard at the next door in to bring in the cleric to follow Westa in.
Things worked differently for the cleric. First off, the smaller your character's stature, the less you can shrink them. Gnomes, halflings and dwarves can only be shrunk once, but they only need once, unlike the larger-statured classes. Shadowstep works differently as well. Bards can cast 'while' moving, but the cleric as well as all other spell casters must remain still to complete the deed, to be running would cancel the cast. I shrunk the dwarf, and positioned him where he was looking through the locked door into the adjacent room and fired off Shadowstep and it instantly blasted him further down the hall. :( I did this a second time and ended further up the hall. :( A third cast blasted him back down the hall again. :( Panicking now, I fired off another attempt and this time it took me into the proper room---much to both my and Westa's surprise! :)
What this would seem to indicate is that the spell is designed to send you in the direction you are running, should you be running---otherwise it will cast you in a random direction. Be prepared with at least a stack of Shadowstep philters in inventory and keep at it till they take you where you need to go.
The rest of the raid went without incident---end result, dead Overking, happy cleric.
Thank you all for your help!

Argent Defender
Incarnadine Breastplate
Incarnadine Helm
Note from Prince Selrach
Singed Scroll
Spell: Aegis of Ro
Vibrating Gauntlets of Infuse
Vibrating Hammer of Infuse

