The most challenging maps for you.

medstrax, I've encountered something similar. This happens on single-player, custom maps, especially if everything is very densely packed, and the author saved space by minimizing free cells. Sometimes, this unforeseen issue occurs where neutral creatures spawn at the beginning of the week in a location that makes it impossible to proceed without cheating: for example, a single cell for disembarking from a boat, and, unfortunately, some gremlins are there! :( Moreover, the probability of this is not that low: it is greater the more densely populated the map is and the longer the game lasts; accordingly, there are few free cells, and eventually, newly spawned neutral creatures occupy a critical position for completing the map.