Order of the Nemesis

This subclass is a repurposing of the UA Ranger Monster Slayer Conclave mixed with elements of the Order of Ghost Slayer. All credit is due to the original creators of that subclass. IMHO the Monster Hunter Conclave fits perfectly with the flavor of the Blood Hunter.

Blood Hunters belonging to the Order of the Nemesis seek out specific vampires, dragons, evil fey, fiends, and other powerful magical threats. Trained in a variety of arcane and divine techniques to overcome such monsters, slayers are experts at unearthing and defeating mighty foes. 

Rite of the Slayer

When you join this order at 3rd level, you learn the esoteric rite Rite of the Slayer (detailed below).

Rite of the Slayer. Your rite damage is force type. The damage you suffer from activating this rite is halved.

Through the ritual of the Rite of the Slayer you have learned to study and unravel a creature’s defenses. As a bonus action, choose one creature you can see within 120 feet of you. This target becomes your Slayers Prey. You immediately learn the target’s vulnerabilities, immunities, and resistances. You also learn any special effects triggered when the target takes damage, such as fire damage halting its regeneration. In addition, the first time each turn you hit your Slayers Prey with a weapon attack, the target takes an additional force damage equal to your Wisdom modifier. This benefit lasts until you target a different creature with this feature or until you finish a short or long rest.

Upon reaching 11th level, any creature you hit with your Rite of the Slayer suffers this additional force damage.

Supernatural Defense

Beginning at 7th level, you gain extra resilience against your prey’s assaults on your mind and body. Whenever the target of your Slayer’s Prey forces you to make a saving throw and whenever you make an ability check to escape that target's grapple, add 1d6 to your roll.

Supernal Surge

Relentless Hunter

At 15th level, you gain the ability to foil your foe’s ability to escape. Your study of folklore and arcane knowledge gives you a key insight to keep your prey cornered. If the target of your Slayer’s Prey attempts to teleport, change its shape, travel to another plane of existence, or turn gaseous, you can use your reaction to make a Wisdom check contested by a Wisdom check made by the target. To use this ability, you must be able to see the target and need to be within 30 feet of it. If you succeed, you foil its attempt, causing it to waste the action, bonus action, or reaction it used.

 

Slayers Counter

At 18th level, you gain the ability to counterattack when your prey tries to sabotage you. If the target of your Slayer’s Prey forces you to make a saving throw, you can use your reaction to make one weapon attack against the quarry. You make this attack immediately before making the saving throw. If the attack hits, your save automatically succeeds, in addition to the attack’s normal effects.