Faithful Hound

You conjure a phantasmal watchdog. Until the spell ends, the hound remains in the area unless you spend an action to dismiss it or you move more than 100 feet away from it. The hound is invisible except to you and can't be harmed. When a Small or larger creature enters the area without speaking a password you specify when casting the spell, the hound starts barking loudly. The hound sees invisible creatures, can see into the Ethereal Plane, and is immune to illusions. At the start of each of your turns, the hound makes a bite attack against a hostile creature of your choice that is within the area, using your spell attack bonus and dealing 4d8 piercing damage on a hit.