Faithful Hound

4th-Level Conjuration
Casting Time: 1 action
Range: 30 feet
Components: VSM (a tiny silver whistle, a piece of bone, and a thread)
Duration: 8 hours

You conjure a phantom watchdog in an unoccupied space that you can see within range, where it remains for the duration, until you dismiss it as an action, or until you move more than 300 feet away from it.

The hound is invisible to all creatures except you and can't be harmed. When a Small or larger creature comes within 30 feet of it without first speaking the password that you specify when you cast this spell, the hound starts barking loudly. The hound sees invisible creatures and can see into the Ethereal Plane. It ignores illusions.

At the start of each of your turns, the hound attempts to bite one creature within 5 feet of it that is hostile to you. The hound's attack bonus is equal to your spellcasting ability modifier + your proficiency bonus. On a hit, it deals 4d8 piercing damage.

On your later turns, you can take a Magic action to move the hound up to 40 feet.

At Higher Levels. When you cast this spell using a spell slot of 5th level or higher, the damage the hound can do increases by 1d8 for each slot level above 4th.

Source: PHB 261, SRD

Changelog

Added upcasting option.
Increased the distance the hound can be from you to 300 feet from 100, and added the ability to move it as an action.