I was under the impression the stalker could cast certain wizard spells like lightning and what not. Valygar can't. I also got the message that he had a weapon that he could not backstab with when he was using his family katana. Any thoughts why this would be?

in my exprince Valygar only gets haste, protect from normal missiles and minor spell turning onces he reaches his spell level three. lighting is cast by the Avenger Druid class. can't help on back stabbing never use it.

I think the reason he can't backstab is he is using Corthala Family Armor which may be classified as plate or chain, which means of course that you can't hide in shadows and therefore backstab. Just a (back)stab in the dark though...

I was under the impression that to backstab, you had to use a piercing weapon(ie short sword/dagger...NOT...slashing...ie katana)
My created stalker carries a plus 2 short sword also in his main hand which I switch to before stealthing for a backstab attempt.withthe quick weapon slots it is easy enough to switch back and forth.
He is only level 9 or so right now and I just scored a 46 point back stab with him and that short sword.
Sorry I don't remember exactly which short sword it is becuase he has 2 different ones besides his +1 katana in his main hand slots....I believe it grants free action too, if that helps....Not that exactly what short sword matters at all....It seems I am rambling after an all nighter of BGII

Backstabbing in the game is not exactly related to PnP rulez. I've backstabbed with a katana before. Course, I am using a Ranger/Thief mix. I think it looks to see if you have a 1 handed weapon and if you are proficient in the thing. I haven't tried 2 handed weapons though as I do not like them. I prefer dual wield. When I went from a Thief to a fighter, it even let me use a hammer. Hmmm. I really don't know how that works except to say that I hit the bloke so hard in the back that it staggered him. Weird rules. I haven't downloaded the patch or anything, so not sure if that may be causing my game to act up weird, but it's kinda cool so I let it play out.

Had a long sword on Yoshimo (%#$@%!$@%^#@$%) and backstabbed a Priest. Natural 20. Pieces of Priest all over. (VERY COOL). Did 64 damage.

BK

Valygar can use stealth in his family armour, and normally you should be able to backstab with a Katana, the same as with any melee weapon a single class Thief can be proficient in. Mind you, you have to be BEHIND the hapless victim for BACKstab to work though.

The Celestial Katana is the perfect assassins blade, for if the immense damage doesn't kill the victim the odds are they'll be immobilised from Celestial's fury.

Sadly, I did not pick up the celestial fury because I was in a hurry to get Imoen. Now it'll be forever before I get it. (Bad script! Let me back into the city already!)

Anyway, backstab works now, and Valygar is really one of the top characters. The leather armor he wears is the second best AC leather in the game, and he is the only one (besides Korgan) who didn't allocate his proficiencies like a fool (i.e. Jaheria). Katanas and spears are the probably two best weapons in the game that are obtainable early on (pre-Underdark).

Or axes, azuredge is pretty nice. Yeah, I wonder why the NPCs put their proficiencies into stupid things. Jaheira's specialisations were terrible. Clubs? Yeesh... spears, woman!

I think it's a penalty for using her. If you want to specialize in spears, you can't specialize in slings or scimitars or quarterstaves. I am certain she was a quarterstaff specialist in BG I.

Minsc's proficiencies have definitely changed. I'm pretty sure he had no idea how to use a bow in BG I. (Though his specialization in maces is also dumbfounding. Why doesn't a single NPC have a proficiency in flails?)