Awakened Camilla

Now that the greataxe has found its hosting shard, the soul of Camilla. Its power seems to be unlocked and increases the stronger the host becomes. Camilla's soul now resides in the greataxe and enables the two to interact. Camilla will refuse to be wielded by any user other than its host and attack their soul. Each minute spent wielding the axe by anyone other than the host will result in the user suffering 1d12 psychic damage. If Camilla gets touched by anyone else than its host it will project horrid imagery into their mind. The axe is incredibly resilient and cant be broken by regular spells or means, if some unstoppable force were to shatter her, the wielder retrieves its pieces and may restore her completely by offering half their health and using a long rest.

Core Ability: Blood-pact

You gain the ability to initiate a Blood-pact with Camilla by sliding your fingertip on the blade. The greataxe then decides how much blood it absorbs. 
You use a bonus action to either roll a 1d8 / 2d8 or 3d8 and then sacrifice the amount of Hit points it demands.
The amount of blood you sacrificed then empowers Camilla. The dice you chose to roll when offering your blood converts to the dice you then roll as additional damage. So 2d8 additional damage each attack for instance.
The bloodthirsty axe always wants to hit something.
On a nat 1 the axe chooses to hit an ally that is no more than 5 ft away from the wielder. Unless the ally succeeds on a DC 18 Dexterity saving throw they suffer Camillas entire damage on said hit.

The effect lasts for 4 turns or until the wielder takes a rest.

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Camilla seems to be able to unlock more if its power the stronger the host gets. And thus scales with the wielder.

At lvl 6:

Camilla links itself to the wielders soul enabling the use of Soul-Link. Each time the wielder rages Camilla benefits from the hosts strong emotion and the host may choose to use one unlocked ability Camilla offers at any point during the rage.

Ability: Camillas-Cry

You gain the ability to enrage the greataxe, enshrouding the wielder in a thick 5ft radius black mist centered on the wielder using a bonus action. The mist causes anyone (allies included) inside its radius apart from the wielder to suffer psychic damage equal to 1d4 + the wielders strength modifier at the end of the users turn.

The mist clears after 5 turns.

The people inside the mist suffer their enhanced traumatic experiences vividly playing in their minds.

At lvl 8:

Ability: Soul-Mirror

You gain the ability to use Soul-Mirror during a bonus action.

Camilla targets one creature of your choosing in a 15ft range to affect with Soul-Mirror. Unless the target succeeds on a DC 16 Wisdom saving throw, they start seeing a reflection of their own soul in the wielder, depicted in the most gut wrenching way. The target gets horrified by the scene and becomes inflicted with the frightened condition.

At lvl 10:

Anti-Flame now burns more intensely. Dealing 1d6 necrotic damage instead.

Ability: Soul-Grasp

Now that your soul and Camilla's have bonded deeper. It is able to always locate you and return. 

You gain the ability to use an attack to throw the greataxe and it will always return to you. The throw has a max range of 60ft and if the hit is critical it lodges itself into the enemy and starts withering away its flesh with a similar effect that can be observed when wielded by someone other than the host. While Camilla is lodged into the enemy it takes 1d6+2 necrotic damage each turn. The axe may be removed by the enemy using a bonus action, once removed it will return to the wielder. The wielder may also choose to recall the axe using a bonus action. The axe takes 1 second to return regardless of distance. Camilla will refuse to travel further than 60ft and will start recalling itself once reaching that distance.

At lvl 12:

Camilla now refuses touch by anyone else other than the host even more. Unauthorized touch deals 1d12 psychic damage. This effect can be temporarily suppressed by the host, letting a singular other person touch the axe without suffering the mental torment.

At lvl 14:

Anti-Flame burns more intensely. Dealing 1d8 necrotic damage.

Soul-Grasp now does not need a critical hit to lodge itself into the enemy and deals 1d6+4 damage each turn. The wielder may choose for it to do so at will.

At lvl 16:

Camilla gets more proficient in weaponizing your blood. Blood-Pact now lasts 5 turns.

At lvl 18:

Ability: Field of deathly paralysis

You may choose to tap Camilla's hilt onto the ground and let a field of spider lilies grow on any surface. The field's center may be placed anywhere as long as its not further than 60ft away from the wielder. The field has a radius of 20ft and the spider lilies are fire resistant. Any enemy creature that touches one of the flowers needs to make a DC 14 Dexterity saving throw or suffer paralysis, armor or clothing does not prevent the effect. At the end of each of its turns, a paralyzed creature can make another DC 14 Dexterity saving throw, ending the effect on itself on a success and becoming temporarily immune to paralysis for the duration. The field lasts for three rounds.

At lvl 20:

Camilla's soul now has fully intertwined with the hosts. Maybe if you found the one that killed Camilla you could feed its remains to the greataxe and avenge her. Doing so will increase Camilla's base damage by +2 during rage and add another 1d8 to the damage increase received when initiating Blood-Pact.

Proficiency with a Greataxe allows you to add your proficiency bonus to the attack roll for any attack you make with it.

Notes: linked soul, Heavy, Two-Handed, Cleave