The Flyby. The blood hound can fly out the reach of a creature without provoking opportunity attacks.

Keen Smell. The blood hound has advantage on Perception checks relying on smell

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

Blood Sense. The blood hound can pinpoint the location within 1 mile of it.

Blood Frenzy. If the Blood Hound takes the Attack action against a creature below its hit point maximum, it can make an additional bite attack against that creature.

Blood Letting. While grappled by the Blood Hound, creatures cannot regain hitpoints. Any hitpoints recovered is redirected to the Blood Hound. If the hound is at full hitpoints, the creatures takes necrotic damage equal to the amount healed.

Life Leech. While grappled by the hound, the target takes 7(2d6) necrotic damage at the start of each of its turns. The hound regains hitpoints equal to the amount of damage dealt.

Airborne Agility. If a creature moves within 10ft. of the hound, it can use its reaction to fiy up to half its movement speed away from or towards the creature. If flying, this does not provoke opportunity attack.
Any movement used this way will result in an equal number of movement speed taken away from the hound on its next turn. (I.e. if the Hound moves 30ft of flying distance as a reaction, then it will only have 30ft left on its turn.)