Enslave Demon

Who has played as a Warlock in hearthstone, may have noticed the abscence of one particular ability. Enslaving demons. I would really like to have a card in the game that embodies this ability. In World of Warcraft, this ability let's you enslave a Demon for a certain amount of time. Sure, Mind Control is in the game, but Warlocks can't use that. (and that effect is permanent)

The enslave Demon spell I came up with is rather underwhelming, but it seems fair to play. For 5 mana, you can take control of an opponent's Demon. Now you might be thinking, what's the chance of playing this on an opponent's Demon, right?  But what would happen if you played this on your own Demons? Then you suddenly get an Demon with haste. You can play an Pit Lord and drop this card on it the same turn.
If this card would be in the game, I would definetly run one in my Demon deck. If gives my control against opponent's Demons and gives me an Charge.