I am currently playing a solo 12/13 Gnome Illusitionist/Thief in an unmodded game (well at least no difficulty adding mods), and am having problems with the demon who's heart I need for the Planar Sphere quest (I believe it is a Tanari). It is him and six or so mephits/quasits/imps.

The problem is that I dont have any saves from outside the sphere, so I need to beat this guy with what I currently have.

The best I can do is kill his mephit/quasit/imp friends by using deathfog+cloudkill+web and running around, getting them to pass through it, but then I am left alone with the Tanari and I can only get it down to injured with Melf's Minute Meteors before he kills me!

Any general tips? If you need more specific info on what equipment/spells I have just lemme know.

I am probably not a good source of advice here, as I have never soloed, but I can throw out a couple of ideas - although a lot depends on what equipment and spells you have.

If you have a +3 weapon, you could try maximum buffing, and beating it to death. A spell sequencer with Blur/Mirror Image and Tensor's Transformation might do the trick.

Can you summon allies? If so, you might be able to summon enough to distract it for a couple casting of Melf's to bring it down.

There are three Tanari in the area -- all three are basically the same. They have about 100 hit points and are immune to fire and electricity, take only 50% damage from cold, have a 50% magic resistance (lower resistance would help), and an AC of -5. And as you found out they hit often and hard.

But they are quite susceptable to acid damage. Melf's Acid Arrow, acid arrows and other such things should help (blackblood club could come in handy if you can hit it -- Tensor's Transformation). Give yourself all the buffs and be sure you are hasted so it never gets near you. If you go the lower resistance route you should have quite a few spells that will damage it (I happen to like skull traps).

Ring of the Ram should cause it damage (you did pickpocket the first one from Tolgeras in the Government Building when you first got this quest like a good little thief didn't you?).

i usually just pound on they with everything ive got.

they arent the toughest demons in the game, least not when i fight them.

Tensers Tranformation, buffs and summonables are good.

i think you can use cloudkill on them too, im not sure, i havent tried it, but if it can a dragon it should be able to at least do some damage to a demon.

you only need one to get out of the sphere.

Interesting, thanks guys. Unfortunately I do not have access to Tensor's Transformations, but I do have a crap-load of acid arrows, melf's acid arrow, and a wand of monster summoning, so I'll just try acid hit and run with summons keeping him busy.

They are not the most difficult boss around, that is sure. You need good defense nevertheless or they will shred you into pieces.

If you have free action (ring or potion would help) they can not hold you with their death gaze. And if you have stoneskins and pro from magical weapons and mirror images, they can not touch you. Now blast away with anything you have, although you may want to lower their resistance at first. I used wands of frost, blast it, run away, blast it again, and run away. It takes some time but they fall eventually.

Or you can just shoot him down with arrows :D , his not really that tough. Just stoneskin/mirror image for protection, haste, equip Tuigan's Bow with acid arrows and then shoot and run. I just tried it and it took me about 12 hits to bring him down. The Death Gaze/Vampiric Touch could be a problem so the ring of free action that Silverstar recommended with a Spell Immunity (vs Necromancy) might come in handy.

I beat him :D

The key was the acid vulnerability, I didn't know about that!

I just used the death fog + cloudkill to rid the place of little winged things, then occupied him with summoned stuff (the little summoned dogs actually damaged him a few times!) and shot acid arrows, melf's acid, and magic missles at him. It was really easy once I knew the right tactic! One crucial thing was to not try using MMM's. The reason was that I had no other means of gaining free action besides Arbane's Sword, which I couldn't switch to if I was using MMM. So I just stuck with arrows and if he threw out a death gaze I'd quickly pause and switch to Arbane's.

You can always use the staff of fire (found in the elemental room of fire) to summon fire elementals to kill the demons. Summon 5 of them, send them in to do their thing, then summon more as they die. The first demon (to the left) is the hardest. If I recall correctly, at least one of the others is not powerful enough to damage fire elementals -- maybe the one at the top of the screen when you go in from the right (go around the edge of the screen counter-clockwise to get to him).

Oh I thought they were all the same? First time I got stuck on this plane I got creamed and badly! After you know how to deal with the fool it's pretty easy though :)