I will keep a list of things I find starting here:
Complication: If you only have 1 available space to summon a creature, and try to summon skeletons. It will not let you click the light up area, and will stay dark w/ the square lighted up until you click a different spell, hit cast, than hit cancel.
-Maybe also, set it up so you can only summon 1 skeleton if there is no other room for the second?