Blurred Movement. Attack rolls against the dog have disadvantage unless the dog is incapacitated or restrained.

Evasion. If the dog is subjected to an effect that allows it to make a Dexterity saving throw to take only half damage, it instead takes no damage if it succeeds on the saving throw, and only half damage if it fails.

Spellcasting. The Yappy dog is a 5th-level spellcaster. Its spellcasting ability is Charisma (spell save DC 15). The Yappy Dog has following spells prepared: 

2nd level (2 slots): misty step

Multiattack. The Yappy Dog use it's unnatural speed to attack 5 times in a flurry of biting.

Action Melee Attack. Bite +7 to hit, reach 5 ft., 1 target. Hit: (1d4 + 1) piercing damage. If target is not under effect of Infuriating yap already, it must make a new saving throw against that effect.  

Infuriating Yap. As a bonus action, the Y.D. emits a supremely annoying volley of barking that makes everyone want to beat the tar out of the little jerk. Everyone who can hear the barking must make a DC 15 Charisma Saving throw. On a fail, all their subsequent actions are focused on killing the yappy dog, to the exclusion of all else, including personal safety, other enemies, and they will hurt friends / party members if necessary to get at the dog.  The target may repeat the saving throw at the end of each round if the yappy dog stops barking, (which it will not do unless something prevents it), or when the target can no longer hear the barking. 

Once the target has made a successful saving throw, it has immunity to Infuriating Yap for 24 hrs UNLESS it is bitten by the yappy dog.

Once the target has been bitten by the Yappy Dog, rage increases. If not already under the effect of Infuriating Yap, target must save per normal versus Charisma. If already under the effect, the target has disadvantage on any subsequent saving throws versus Infuriating Yap.

While under effect of Infuriating Yap, victim has disadvantage on all rolls for actions and checks  not directly related to killing the yappy dog.

Attacks from creatures other than the yappy dog have advantage against anyone under the effect of Infuriating yap, as the target's focus is completely on the yappy dog. The save throw vs. Infuriating Yap may be repeated whenever character takes damage from an enemy other than the Yappy Dog.

Dominate canine - once per day, can attempt to take control of any canine type monster, including shape shifters in the form of a canine. While under the Yappy Dog's control the target acts as its loyal follower, obbeyingits telepathic commands or anticipating its needs when applicable. Target get's DC 15 saving throw to resist, once the target has successfully saved it can not be targeted again with 24 hrs. Can be released by remove curse or dispel magic.

Uncanny Dodge. The Yappy Dog halves the damage that it takes from an attack that hits it. The Yappy Dog must be able to see the attacker.