The Hollower Series by Mary SanGiovanni

The Hollower's sole purpose is to stalk, to torment and to drive its victims to their deaths. It can sense each victim's weaknesses, change its appearance and strike however it will hurt the most. Dave Kohler is about to fall prey to The Hollower.

Erik McGavin finally has his life back from the monsters who sought to destroy him inside and out. He has come from having nothing to having a happy, stable life with his beautiful wife, a home, and a baby on the way.But there are signs the rift has opened again, and that what has come through this time is the ultimate deadly force: the Three are looking to cauterize our dimension, and have powers beyond anything our world—or theirs—have ever seen.