Pain-Possessed Constructs

You may pay {p/b} as you cast an Artifact Creature. If you do it gains "Haunt. When the creature it haunts dies, Detain target creature and target creature gains a +1/+1 counter"
When a creature that is being haunted dies, you pay {p/w} and if you do, return the creature that was haunting it on the bottom of your library.