It can be a nasty "Trap", but I was walking thru Katta around the corner between Baking supply place and Smithing Supply...and all of a sudden, "a Coterie Assassin" appeared (was blue to me, I was 51, then)...suprised me so much, I couldn't think straight to cast the right spells...and he killed me.....
Scary thing, I ran back to get my corpse, and the same thing happened, he popped again....still, naked as a woodnymph, I didn't get him....
Only thing I can think of why he spawned was, I noticed the two guards that usually guard that entrance were gone(?) Like he killed them, and that was a sign there was a Coterie Assassin near....pretty neat little "event"..but dangerous if you don't know about it...the person who submitted this item must have killed the assassin and got sleeves...btw, from the picture in the Fashion Tables, Coterie looks cool on Vah Shir (especially with the stripes cutaway patterns on the females...like black with light stripes, or something)...anyway, this is as black as Gnome Skin when yer in the dark, but in the light, it's got a hard to notice (blood?) red tint to it...very cool...