"Necropolis" - changes to creatures of levels 6-7.

3) But now, the demand for it should increase if we don't remove it.

There might be a demand for a platinum car, but it's unlikely. The price is very high, considering the rarity of mercury – no one has such a resource advantage as the undead do with mercury. It's unlikely to be overpowered; getting a good bonus for such a price (if you can afford it) will only be a pleasant experience. In any case, there's no need to rush to remove a building that is rarely constructed. Practice will show whether it's overpowered or not.

If the Necromancer happens to have a lot of mercury, it will become a clear overpowered unit. Currently, the Messengers are almost no different from Cyclops in terms of attack and damage, except that they have less defense and health, but their counterparts are clearly stronger, weaker in melee combat, but have an enhanced ability. The price is accordingly increased.

The Cyclops itself is one of the weakest units in its tier, if we don't take into account the racial and super-physics of the Barbarian, which the Necromancer doesn't have.