In the South West tower of BoT first room on the left, Galm spawns in the far left corner by the bed. He is a caster and was noticeably easier to kill than the Kriger Placeholder. He will gate at low health if you move him away from his spawn point and do not prevent him casting.
He looks to be in the East Wing of BoT, I don't think I've seen him in one of the towers persay. But I could be wrong too, haven't been up there in awhile either.
We found Galm in the Water Tower, left side room... he has a PH, doesn't hit that hard, but uses druid spells... can't remember what his max dmg is, already cleared my log of the fight.
We pulled 2 sets of weatherbeaten shoulderpads off him, and an ornate chain helm also in about 8 hours of fighting in the tower
Vlade Darkstalker 65 Overlord, Officer of Twists of Fate, Povar