I was in Lower Guk just last night... at least I thought it was. It was
my first time down there. As I finished zoning, it said 'You have entered
old ruins of guk. (is that lower guk?)
I zoned in as a higher level dude was slaying a shin ghoul knight; the
very mob (one of) from which I need to loot a lambent quest item. I had my
invis song going as per usual. All through upper I noticed that everything
was indifferent to me. YAY! Ok, song is working like a charm. I did manage
to con the shin ghoul knight while he was being attacked. "A Shin Ghoul
Knight scowls at you, ready to attack. What would you like your tombstone to
say?" Um ok, first reaction is to zone, especially since he was just inches
away from me. The guy was using the zone line as a buffer, apparently. NP.
Zoned... Went LD... That's where I am as it stands.
So, at 19 so far, from what I think is lower (?), can see through invis.
Now, whether or not your invis ability increases as you level or not, is
something i know zero about.
All I know is I was happy to get invis so I can get down to lower guk to
get these items (shin greaves and gauntlets) before i had a chance to either
go hunt there for exp, or get some faction hits somewhere else.

Pava, Bard of the 19th measure
Silent Dragons
Cazic Thule

>Hmmm, I will have to give this a try in Lower Guk. I really need to learn
>that place better.