So I cant really find anything about if a unit can be affected twice by basically the same Endless spell, and my experience in general is that abilities/rules stack, unless specifically stated otherwise. Basically, imagine bound Geminids on the table. We win priority roll and take the turn. We move them prior to a new battle round and affect unit X with -1 to hit. In our hero phase we dispell the Geminids, then cast it again and move the Light over unit X again, resulting in -1 to hit again. Is there anything that prevents this from stacking, so that unit X suffers both 2D3 MWs and -2 to hit?