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

And if you simply compare it with level 7 of other factions (Nival Interactive still intended some kind of balance, but now level 7 is clearly strengthened)

Added 2 minutes ago
On the third week, if resources are scarce, you build it on the fourth week, but I usually play on the forest map because it's faster, but you need a lot of wood.

So, on the third week, you build level 7, add an upgrade to it, and also build an additional structure? And what is the difficulty level?

For some factions, you can build level 7 as early as the second week, which means +2 additional creatures compared to the third week, which is the same as the additional structure you build in 2 weeks.