As part of "The Cheap Bastard's Guide to LIVAN", I thought i'd just release this bit until the guide is done.

MUSTARD GAS - YOUR FRIEND
A mostly disliked item due to characters being dissolved by a nigh-invisible cloud of lingering mustard gas formed by the character throwing said grenade and forgetting about it. However, with the right info, you can turn this deadly contraption into a money making, looting (and ass-saving) machine!

Starting Off
1) Stock up on dwarven gas grenades full of mustard gas. Any and all you find should be picked up and stored in a container to prevent them from exploding on you due to the enner or mines or whatever.
1a) OPTIONAL: Getting Ivan's gas mask will help ensure you don't get dissolved by accidental gas exposure, but any kind of gas immunity will do. Not necessary provided you are careful and check tiles with (L)ook.
2) Having and END of 10 (e.g. HP = 37) gives you a very low chance of surviving the effects of mustard gas should you be exposed to a cloud without protection. Raise END at least 2 levels if you can't be bothered being careful or obtaining gas immunity.
3) Although not the best use of a wand of cloning, having this and a few scrolls of charging will help raise your supply of mustard gas grenades. Just use the same technique as you would for scrolls of change material: Place 4 grenades on the ground, step 1 step away, zap them, charge wand if needed, zap again, repeat ad infinitum. And you are going to need a lot if you want to take on Attnam or Mondedr. The least you need to make the Dwarven Vault reletively safe is 21, and even then there are 3 people left (The shopkeeper and 2 dwarven guards).
4) SHOULD YOU BE EXPOSED TO MUSTARD GAS WITHOUT PROTECTION, R(U)N OUT OF THE CLOUD AND REST (h) IMMEDIATELY.

Putting The Grenades To Use
The best part of using mustard gas is that if you kill somebody with it, the game does not determine it to be your doing. That means you can "assassinate" people and steal their stuff.
In short, all you need to do is find your target, and throw the grenade at a wall next to them. This results in the gas spreading out, engulfing the unlucky sod and ensuring a slow and painful death.
e.g.



Y = you and X = Your target and O = The wall you must throw the gas grenade at to kill the target via gas.

Using this method you can do the following:
1) (possibly the most useful thing ever) Eliminate most of the people in Attnam to make winning the game easier. You can't get Petrus of course, and anyone who isn't standing near a wall is harder to "assassinate", but not impossible (as detailed later). Possibly the most usefull part of using mustard gas in attnam is that you can kill those 2 damn mystic frogs and Haedlic Gaedon.
2) Murder shopkeepers to steal their stock. Don't worry about shop guards, they don't mind if you take things so long as the shopkeeper isn't around. If you are using this against the shopkeeper in Attnam, make sure to kill the slave with gas first, or he will take most of the stuff in there and make a run for it. Or you could buy him I guess...
3) Kill the librarian! (After science talking and using the "library trick" to suck his gold dry of course) And steal everything he owns.
4) Kill everyone in Decos's chamber (excluding decos himself)
5) Sterilize most of the dwarven vault and gain 2 illithium gauntlets of strength +4, an octiron plate mail, 2 unique weapons, the blessed shield of the phoenix, the golden shirt of the jaguar (haste, polycontrol, and telecontrol), a spider silk cloak of electricity resistance, a diamond belt, 2 adamant boots of strength and much more! Very useful for those not interested in getting their INT up.
6) Teleport a pile of them in the enner's lair. He doesn't stand a chance.
7) Get that helmet of piercing perception off the patrol guard in Attnam

DIAGRAMS!
Added in the attachments. The red spots on the walls are which walls you should throw the grenade at to be most effective and economic (by that I mean use less grenades). The blue part of the red dot shows what direction the wall should be hit from (so you need to hit the wall with the grenade on the part where the blue is on the dot). Green spots are walls that should be hit after you're done with the other spots and should only be done provided no one is in the way. Please note for Attnam many of the spots require you to be in the mustard gas after throwing a grenade. Gas Immunity is highly recommended.

Does the slave really grab the stuff and run? That's pretty funny, I never noticed.
Also, once you kill the dwarves, can you just take all of the equipment from that vault? Or would you just have all that equipment and then be forced to flee Attnam/take on Petrus?

Damn, I tried zapping a wand of door creation behind Petrus so that I could then throw the grenade at the door but it pissed them off. Also, mustard gas doesn't seem to have much of an effect on Petrus. Even having him stand on the gas square continuously for many turns, he dropped 3 hp but no lower.

That's damn good! Makes me wanna actually touch some IVAN beyond version 0.50!

Guides are fun. "Cheap bastard's guide" makes it sound like Paladin Press.

Yup the slave grabs what he can and either rushes for food or goes out the door.

Once you've "removed" the dwarves from their vault in Attnam, taking anything still counts as an act against petrus (alarms and so forth, death closely follows).
However, you're free to take the items out of the dwarven vault in GC because they're a different team in the script. Just make sure you can take out 2 dwarven guards
Oh, and the shopkeeper doesn't seem to care about the vault, so he won't attack you.

Diagrams are finished for Attnam, New Attnam and the Dwarven Vault. I just have to move them off my "IVAN Computer" and upload them.

You have a computer just for IVAN?

Talk about dedication...

Wow, this sounds like a powerful exploit to me.

Petrus not losing many HP may be because of his extremely high endurance... he might just be healing so fast that it counteracts the gas' effect.

Guess I was mistaken about Petrus. I think it's because the gas didn't actually explode on him, he only walked through a cloud. I think this should definitely be considered an exploit.

It's an old computer and the most "advanced" game it can play is Deus Ex
I mostly use it for old games (yay DOS) or those not graphically demanding, but mostly for playing IVAN because my other computers have more recent games to play

Some wierd stuff have happened after killing Decos with Gas Granade. After the assasination I challanged Ming Pong for Levitation Belt and won. Some kind of wicked invisible wall appeared in place that normally Decos stands to give the player a T-shirt. I was able to talk to the wall (and it had Decos responses) and use stethoscope on it, but I did not get its stats, only "You hear coins clinging" or something. The phantom Decos-like wall was not moving, just standing there. Finally I decided to leave, but it corrupted my save file and the game itself.

Huh, that's really weird, indeed. I guess it's never been noticed before because Mustard Gas is relatively new to IVAN. Great find.

try taming phantom decos

You can't tame him to begin with. I doubt you can tame phantom Decos.

How about scaring him with a horn of fear? Will he leave items when zapped with a wand of striking? Poisoned from skunk-farts?