I’ll bet he is the least important of the lieutenants and the first to die. Not based on anything in particular. Just a hunch.
If he’s the General, then it does sound as though we’ll at least meet him first, at Moonrise Towers. I’m forgetting the details we’re given, but iirc it would make sense he’s there given I think Halsin says the shadow curse around it was linked to the battle against him by druids and Harpers back in the day (was that around 100 years previously?). I’m guessing defeating him will also cure the shadow curse. But even if he’s BG3’s Mulahey, I’m not sure that’ll make him the least important, perhaps just the first met amongst equals!