A few great places are on the entrance to the doorway to B on asylum (like in the first vid) one of the back wall of A on rusted lands (through the hole in the wall) also, the iron pillar on B (also on rusted lands) and the wall closest to the water on C (again, on rusted lands). Just off the top of my head those are the most common places ill throw one. But any wall where there is an enemy nearby will usually kill them