- A reference guide and manual in Russian for Heroes 3.

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q12

No, it's a regular map for Heroes 3, called "Blood! A Vampire's Tale"...

No, it's not a regular one! Although it's not a WoG map. I found it in the map folder: the Russian name is "Blood! A Vampire's Tale"; it's also for the RoE version. Not a regular one - because it's not one of the standard maps, but an author's map. Such a large number of creatures can only be found on author-made maps; the game developers weren't obsessed with gigantism.

...but the left hero's necromancers still have quite a few, why isn't there an overflow? Initially, the right hero had an army of over 300 liches in one cell.

The map author simply wasn't concerned about the overflow problem, or he didn't even know about it (like you still do:)).

Воскресайте, камінні душі, Розчиняйте серця і чоло, Щоб не сказали Про вас грядущі: їх на землі не було…
(Василь Симоненко. Люди – прекрасні)