As long as you control a Hound, at the beginning of each player’s upkeep, destroy each Demon that player controls unless he or she pays for that Demon.
Ghoulcaller's Flail {4} |Artifact| Spirits you control get +0/+1. / As long as you control a Hound, at the beginning of each player’s upkeep, destroy each Demon that player controls unless he or she pays 1 for that Demon.