MIY
Throw away theory for those who care to read em:
Because we have seen Abby appear in the spider webs like she was being held captive.. maybe the Abby Boyd shot was just the MIY shapeshifted into her form? His last attempt at causing everyone to turn against each other, thwarted by Boyds ability to stop her(like if he is the one that massacres in daylight it sort of fits?). Maybe why there was a long "peace" period. Maybe thats why Boyd is receiving visions of Abby now. She wants to warn him?
Or the visions of her come from the spider entity like with the ballerina when she appears to try and convince Boyd to stop when smashing the box.
Just some food for thought i dunno