But mostly, it's around 200+. When playing as Necropolis, I mainly used a classic tactic: 3 heroes with necromancy, each leveling up skeletons in 3 different locations. One with a stack of skeletons and level 1 units, another with 3 liches, and a third with vampires and level 1 units.
On level 141, I consistently had 800-900 skeletons, without any amplifiers or using Izry/Vidomina.