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

The icons for Dragon Week should be dragons, but the undead increase; for Undead Week, the icon should be undead, but the knight increase.

That's not good. So, we replace the undead icon with the black knight icon, first saving it under a different name, and then in Visual, we give the undead a link to it, so that everyone still has their own icon. It's even simpler with Dragon Week.

In any case, the texts need to be reworked, and the Bone Dragon Week should be removed.