Lightning Spire bolts are
size 2 and have Last Collide enabled, so although they aren't destroyed on collision they normally only collide with the
Sorceress once (as indicated by equipped items applying 100%
Chance to Cast Nova When Struck). However, when a
Desert Mercenary is close enough adjacent for a bolt to collide with both of them simultaneously,
he then becomes its last target and the bolt can collide with her a second time before it is out of range.