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

Okay, I just checked in the game and specifically looked for neutral creatures, and I only deployed 10 banshees. With a Block Damage (BD) of -16, the damage was only 1500, not 2600 as expected. I thought the +/-5 limitation only applied when calculating the probability of the BD effect and luck (or rather, unluck) triggering, but it turns out it applies here too, so everything is fine now.