The lights are on, and Virgil's home

I take it he's not using any lamps or that glowing helmet ?

That's probably some spellcasting FX that got stuck. If it's light, then it mihgt actually help him until he becomes expert at melee. Then it will keep helping your opponents that are not expert at anything.

I had that happen a couple of times, once upon returning form old sewers under tarant, I realized thet Virgil was glowing and had some blue blob stuck to him. I had to load an earlier save to get rid of that.

I've no idea how to get rid of that though. Maybe let him die and try ressurecting him if the light goes away after he's dead. If not, drag his body around to light dark places. Or try to stand it all the way until he leaves you at Qintarra, the effect will definately be gone when you pick him up in Caladon.