You'll need at least +1 weapons equipped (preferably something you are proficient in) - there are heaps scattered in the Vale of Shadows. Offensive magic will also do the trick.

I had the same problem, so I've bought three +1 weapons but I'm still unable to kill the shadow. What am I doing wrong?

Originally posted by borisjohnson:

i have big trouble finding a way to kill a shadow in the vale of shadows i have killed the lesser shadows no problem but when i fight a shadow it keeps saying weapon ineffective
HELP

Just experienced that. Shadows, Imbued Wights, Mummies, and some mini-Bosses are immune to non-magical weapon.

Non-magical weapons - standard weapons and bullets
Also non-magical are "high quality" weapons which have +1 +2 to THAC0 but no bonus to damage. Usually its slightly green-colored

And Magic weapons are +1, +x titled weapons, they had that +1 in THAC0 and in damage.
True Magical +1 War Hammer, +1 Bolt, +1 Arrow WILL damage these creatures.
Its reminds Silver weapon to damage ghosts in Elder Scrolls games.

Also literally magical damage also works - Spiritual Hammer (Cleric spell), weps with elemental damage and spells.

Never had this problem. Shadows and lesser shadows always went down, no problem, with my party's ranged weapons. I remember this clearly, because my goal was to take them all out before they could close to melee contact. I'm wondering if it was because I already had +1 ranged weapons or ammo for everybody (unlikely) or some other reason.

EDIT: Apologies --> Just went to VoS on a new playthrough and tried to clear all the outside areas before going into any tombs/caves. {minor Vale of Shadows spoiler --> } All the shadows I ran into at the start were Lesser Shadows, but, towards the end (in the SE corner, with about 95% of the map cleared), I ran into a (not lesser) Shadow. My weapons were ineffective. I think the reason for this (and the reason I did not notice this before, which is the solution to your problem) is that the game expects you to pillage a few tombs before you get this far, and therefore have some +1 weapons.

Also, remember that, for some monsters, you need +1 ammo to affect them: A longbow+1 shooting normal arrows might not affect a monster, whereas a normal bow with +1 arrows might. I don't think you will have that problem this early in the game, but something to keep in mind.