Invis potionsFollow

The vendor is directly west of the PoT stone, he is named something frostsomething. Cloudy potions are what you're looking for.

Shammys can make Essence of Concealment, but the cost of components is much greater than Cloudy Potions which almost any BASIC Alchemy vendor has for sale. One drawback to Cloudy Potions is you cannot combine them into doses of 10 (as far as I know).

A few places that sell Cloudy Potions that I know about:

Merchant outside Kelethin Bank.

Merchant on the Island just inside West Cabilis from East Cabilis.

Barbarian merchant inside a building in PoK near the Qeynos Stone. On that side of PoK anyway, one of the buildings in the middle. Door opens on the library side. Go straight in, if you see the barbarian you are there.

With good charisma, Cloudy Potions are around 10pp.

There is a potion vendor in every town in norrath. They sell the same basic 8 potions on each one, including cloudy potions. Cloudy potions cost ~10p per dose.

There is another dropped potion called a potion of invisibility, also 1 dose. Other common charged invisibility items include Mantle of Stealth (2 charge), and Larrikan's Mask (10 charge lev. 45 required). Gnomes can tinker a Gnomish Vanishing Device, rechargable! but not cheap.

Yup. There'll be a cloudy potion on sale on a vendor in pretty much every town (haven't looked in every town, but I'd assume there is).

The two places I most commonly buy them is the gnome in the lighthouse in Gunthak, and the potion seller in the building near the ZO in PoT (in the bank building I think).

This is purely due to convenience. If I'm travelling into LoY, it's worth 10pp or so (bit more with my dwarvish good looks!) just to avoid the hassle of dealing with a zillion green mobs beating on me. It's usually a good idea to buy one for the return trip too (even though you can usually find a druid to get you out, I don't assume that'll be the case). Sometimes you need invis to get to camps in various PoP zones (BoT springs right to mind). So I've learned where the potion vendor is near there.

I'm sure if you look around, they are available pretty much all over the place. I just don't need them that often. There really aren't that many places in the game that you simply can't get through without an invis. Those few are a PITA though...