about troop separation and sacrifice

[jwallstone]

They will go out of control. Your total number of horsemen including all stacks is what counts

This does not count summoned units (like thorns), phantoms, or hypnotized or magically controlled units.

[Razorflame]

hmm too bad

[Vilk]

In fact from the start you cannot do two stack of a same unit that has a sum over your control for one pack. The example you gave was ambiguous about that.