Heroes 5.5 WarGame Edition - Tactical Edition.

Actually, version 3.1 is currently in effect, because before, the Necromancer would receive the Prayer spell as a summoning spell...

This has never happened; it must be some other mod.
Currently, the mod uses the old concept (see the first post in the thread).

Added 11 minutes later
By the way, there's an idea to compensate for the Orcs' dead "Magic" stat. Each day, they would receive a random temporary bonus until the end of the day: +X to attack, defense, or knowledge, where X is the Orc's Magic value (like the Orc's power is overflowing and temporarily increases their stats).