"I still don't understand how any of that is possible," I muttered.

"Think of toilet tissue. You have a top layer and a bottom layer. They are the world of the living and the world of the dead. But all those ply pieces in-between, all those thin sheets that you can't see, but are there, adding thickness and a wholesome wipe, imagine those being the places that exist between the living and the dead. They touch, and in places, the barriers can tear; the twins' mother used her magick to create tears to allow her beasties through. But it took too much energy. Too much power. The creatures would sleep...