Keldorn lvl 13

me lvl 14

Minsc 12

Aerie (dual class) 11 and 12

Jaheira (dual class) 11 and 13

Imoen (dual class) 14 and 7

I am in the Underdark. I wanted to kill the Balor, but unfortunately i couldn't do it so i resolved to killing the gnome lord which made me sad cause they were all nice to me

Am i underleveled?

Playing on Core Rules.

To kill anything in Baldur`s Gate bigger than a rabbit or squirrel, until these are mages turned to animals, you need strategy. Find out week points of Balor and attack from all sides, with whatever works.

U could upload save here https://gofile.io/welcome,
that way it would be fun to play this situation in exact, if you like

Can`t say that you are underleveled, there are two multiclass Aerie an Jaheira, most experience is divided by 8 that way.
In my way you could have any level at this moment it is just power-gaming isn`t that much fun.
I like that you are going to darkness unprepared, I`m doing same in all rpg and always improvise with whatever is founded... and darkness is always surprised ^
There is interesting thing with NPC level, the more experience you have when inviting a member, the more experienced member would be invited (up to limits)

Core Rules +1 : )

Cast resist fear and haste before the fight with the balor. Have your party members with these buffs attack the balor. Pull out anyone who gets low on HP. You can just tuck them away in a tunnel.

I don't think your party is underleveled, they seem to be about as experienced as the game is balanced for at this location.Core rules is harder than normal difficulty.

You're in the right range as far as raw levels, but you may still be underpowered based on your gear. Balors are tough -- without some solid defensive equipment and a lot of magic items, you will struggle with the fight regardless of level.

Also keep in mind the game is balanced for "Normal" difficulty level. If you're playing on "Core Rules" then you're one difficulty level higher than intended and the game will assume you already have a solid foundation of knowledge and tactics. If you're doing a first-time blind playthrough on Core Rules, you will most likely run into some challenges that you won't be able to overcome without a lot of trial-and-error or maybe even rolling back to a prior save state and making different choices.

Imoen can just STEAL the gem from the gnome, as a third option.

Well i tried but she has too low pick pockets. I used Yoshimo before, and he would certainly have been able to take the gem. Unfortunately Imoen was out of my control for 2,5 chapters so...

So you have to save, and reload when she fails.
I didn't mean it's guaranteed success, or not annoying mechanic. I said, it is an option if you can't fight the demon, but don't want to kill the duregars.
Notto mention, you can improve your chances to Yoshimo-level if you give here the Gloves of Pickpocket, and/or a couple of Potions of Master Thievery.

Unless of course you avoided shops like plague, and picking up items.
The game begs you to check your items in various ways, so you should notice unidentified objects.. If you dismissed all the hints given, that's where you end up.

Btw, I'll keep an eye on your posts, I'm VERY interrested if you'll beat even SoA, not to mention ToB. You'll either fail spectuacularly, or overcome your difficulties and give a good story.
Either way, we, your audience win.
I hope you win too.

If I may, what's the games you usualy play with? Both for curiosity, and maybe to be able to give out adivces better suit your playstyle. We wish your success.

Not sure whether it's the right files i uploaded https://gofile.io/d/91iBS8

There is a 95% maximum success rate, otherwise it is the chance your character has on it.. Sneaking is the only skill I'm aware of negative modifiers by the sorroundings (sneaking from front gives you a negative, sneaking out of shadows give you a negative etc.).

And yes, I've asked what genre of games you usualy play.
You obviously not got used to reading manuals, so my guess is, BG is a wee bit different than what you got accustomed to.

PS: those are the right files.