Dark leash

You’ve received the dark gift of a Hound of Ill Omen. This creature of shadow and dark magic was either granted to you by a practitioner of shadow magic or has begun haunting your steps. 

For a number of minutes equal to your proficiency bonus, the shadow hound will follow your commands.

But the longer it spends outside of the Shadowfell, unless dismissed, the greater the chance the hound may attack another creature at random unless its summoner can succeed on a DC 15 charisma check. 

To summon a shadow hound, roll a D8 for greater than 4. If you fail to summon the shadow hound, you cannot attempt it again until the following day.