Sacrificial Prison

Hexproof
When a creature dies, instead of putting it in a graveyard or exiling it, attach it to this card. If
the creature had counters those counters are not removed. If the creature was a token it is not destroyed.
At any time, any player may sacrifice a creature
and unattach and gain control of a creature
attached to this card.
I am loyal to no man now, that place has stolen me.