The Hexbeast

You have made a pact with rogue summoned beast, although you have learned that it is not the creature itself, but a dark hex that has bound itself to the summon and now you as well. The dark being has offered you great power; as your power grows and changes so too will the beast bound to you. Hexbeast warlocks rely on their hexbeast which not only serves as a companion in their lonely lives as dark conjurers but as the very source of their power. A Hexbeast warlock who has lost their Hexbeast is no more than an average man who has once tasted true power. Those that make eternal bonds with their hexbeast, however, are an unstoppable duo. 

The Hexbeast is treated like an animal companion, it can understand your desires and vice-versa, but its ability to understand language is reflected in its current form. The spells of your expanded spell list can be used to summon the Hexbeast in a new form. The Hexbeast is your source of power, when it drops to zero hit points it will retreat to a pocket dimension to be re-summoned, but once it leave your plane of existence you can no longer use your remaining spell slots until it returns. (Ritual casting find familiar can bring back your Hexbeast, but it’s initial form must be from the find familiar spell until you can use a second spell to change it. Higher level spells have durations of the summoned form, after the duration your Hexbeast will return to its last non-duration form.)

Expanded Spell List

You have been granted an expanded spell list to change the form of your Hexbeast.

1st- Find Familiar

2nd- Find Steed

3rd- Conjure Animals

4th- Summon Greater Steed

5th- Conjure Elemental

6th- Conjure Fey

Knowledge of forgotten battles

This is not your Hexbeast's first life. He imparts his knowledge of battle to you, allowing you to gain proficiency in medium armor, shields, and martial weapons. It does him no good to lose his only living servant. 

Hex of location

Your Hexbeast is skilled in locating the vitals of his enemy once he has attacked them. You have advantage on hitting an enemy if it is the last creature that your Hexbeast damaged. Also, your Hexbeast can track down the last creature it damaged as if using locate creature.

Symbiotic Blood

You and the Hexbeast are now connected by pact and in blood. You can use a bonus action to sacrifice HP to your Hexbeast to heal him the same amount.

You can now cast spells, on your turn, from the location of your Hexbeast as long as you can see it and it can hear you.  

Desires of the Hexbeast

The bond between you and your Hexbeast has grown. Choose one of the bestial desires to give in to. As a bonus action you can activate one of these abilities when your Hexbeast is less than 10 feet from you and may use it as many times as your charisma modifier (at least 1). This resets at dawn.

Hunger of the Hexbeast: If you drop an enemy to zero health points then you may take another action.

Thirst of the Hexbeast: If you drop an enemy past zero health points then you may gain HP equal to how much damage the enemy took past zero. 

Greed of the Hexbeast: If you drop an enemy to zero health points, all of the equipment they are carrying is transported to the pocket realm. It must be summoned back within 3 days or lost forever.

Hexbeast possession

Your Hexbeast uses an action to touch a creature in attempt to posses it. The Hexbeast must succeed a charisma saving throw with a DC of 10 + the creature CR or the spell fails. If the creature is successfully possessed then he will obey any command short of harming itself intentionally. The spell lasts for 1 minute multiplied by your charisma modifier, afterwards the creature must make a wisdom saving throw against your spell DC or stay possessed. If the creature dies, while posses, then your Hexbeast will be dropped to 0 HP.