Maximillion  

Could have just been coincidence... after half a dozen or more cycles of killing the static bats at the bottom of the tower and 2-4 roamers that I noticed he never spawned. Next cycle I was more attentive and went ahead and killed all the static grayfang bats (ignored the level 1 bats) and pulled all the roamers and killed them. The instant the last bat died, Maximillion popped on the spiral ramp.

I don't think it was coincidence, since the static bats should have been the first ones to pop, but since nobody else has noticed this in the 2 decades since this expansion came out, it seems unlikely that an obvious spawn mechanic like this would exist without having been documented.

Is he killable by one group of 70's or do I need more people to take him down?

spawn loc:

drops

http://lucy.allakhazam.com/item.html?id=83412