KalistaA specter of wrath and retribution, Kalista is the undying spirit of vengeance, an armored nightmare summoned from the Shadow Isles to hunt deceivers and traitors. The betrayed may cry out in blood to be avenged, but Kalista only answers those whose cause she deems worthy of her skills. Woe betide those who become the focus of Kalista's wrath, for 
any pact sealed with this grim hunter can only end on the cold fire of 
her soul-spears.
Lore
In life, Kalista was a proud general, niece to the powerful 
king of an empire none now recall. She lived by a strict code of honor and expected others to do the same, serving her king and queen with utmost loyalty. Her king had many enemies, and when the rulers of a conquered land sent an assassin to slay him, only the speed of Kalista's sword arm averted disaster. But in saving the king, she damned the queen. The assassin's deflected blade was envenomed and sliced the arm of the king's wife. The greatest priests, surgeons and sorcerers were summoned, but none could draw the poison from the queen's body. Even the king's magic could only slow its progress. Wracked with grief, the king dispatched Kalista to quest for a cure. Before departing, she tasked 
Hecarim of the Iron Order to stand at the king's side in her stead. He reluctantly accepted this task, bitter at being denied the chance to join Kalista.
Kalista traveled the world, seeking a cure from learned scholars, hermits and mystics, but always without success. Finally, she learned of a legendary island beyond the ken of mortal eyes, a place said to hold the key to eternal life - the Blessed Isles - and set sail on a last voyage of hope. The island's inhabitants knew of her quest and, seeing the purity of her intent, drew her boat to the shores of their island. Kalista begged them to heal the queen, and the master of the order instructed Kalista to bring her to the island, where they would cleanse her body. As Kalista boarded her ship, she was given arcane words to pierce the glamours protecting the island, but was warned against sharing that knowledge. Kalista sailed for her homeland, but arrived too late; the queen was already dead.
The king had descended into grief-stricken madness, locking himself in his tower with the queen's festering corpse. Her uncle learned of Kalista's return and demanded she tell him what she had found. With heavy heart, for she had never before broken her oath to the king, Kalista refused, remembering the warning given to her and knowing there was no purpose in bringing a corpse to the island. The king named her a traitor and imprisoned her until such time she relented. There Kalista remained until Hecarim convinced her to tell the king what she knew. He urged her to let the king find peace, either in his wife returning to him or in finally accepting she was gone and allowing her to be buried on the Blessed Isles. Between them they could assuage the king's madness and bring him back with no harm being done. Hesitantly, for she sensed something amiss in Hecarim, Kalista agreed.
And so the king sailed for the Blessed Isles with a flotilla of his fastest ships. Kalista spoke the mystic words to undo the veil shrouding their destination and the king cried out as its glittering coast was revealed. The king marched towards a distant white city at the centre of the island where he was met by the master of the island's guardians. The king ordered the man to bring his wife back from the dead, but was told that trying to cheat death went against the natural order of the world. The king flew into a fevered rage and commanded Kalista to kill the guardian.
Kalista refused and spoke of the great man he had once been, but her appeals fell on deaf ears and he again ordered the guardian's death. Kalista called on Hecarim to stand with her, but Hecarim now saw a chance to realize his long-simmering ambition of replacing Kalista as the king's favorite. He stepped towards Kalista as if to stand at her side, but instead drove his spear through her back in a monstrous act of betrayal. The Iron Order joined him in treachery, their own spears plunging into Kalista's body as she fell. A brutal melee erupted, with those devoted to Kalista fighting desperately against Hecarim and his knights. Despite their courage and skill, their numbers were too few and Hecarim's men slew them to a man. As Kalista's life faded and she watched her warriors die, she swore vengeance with her dying breath upon those who had betrayed her.
When next Kalista opened 
her eyes, they were filled with the dark power of unnatural magic. The Blessed Isles had been transformed into a twisted mockery of life and beauty, a place of darkness filled with howling spirits condemned for all eternity to the nightmare of undeath. She knew nothing of how this had happened, and even as she clung to her last memories of betrayal, they slowly faded until all that remained was a thirst for vengeance burning in her ruined chest.
A thirst that can only be slaked in the blood of traitors.
- Invocation
The sword-wife stood amid the burnt out ruin of her home. Everything and everyone that mattered to her was gone, and she was filled with fathomless grief... and hate. Hate was now all that compelled her.
She saw again the smile on his face as he gave the order. He was meant to be their protector, but he'd spat upon his vows. Hers was not the only family shattered by the oath-breaker.
The desire to go after him was strong. She wanted nothing more than to plant her sword in his chest and watch the life drain from his eyes... but she knew she would never be able to get close enough to him. He was guarded day and night, and she was but one warrior. She would never be able to fight her way through his battalion alone. Such a death would serve no purpose.
She took a shuddering breath, knowing there was no coming back.
A crude effigy of a man, formed of sticks and twine, lay upon a fire-blackened dresser. Its body was wrapped in a scrap of cloth torn from the cloak of the betrayer. She'd pried it from her husband's dead grasp. Alongside it was a hammer and three rusted nails.
She gathered everything up and moved to the threshold. The door itself was gone, smashed to splinters in the attack. Beyond, lit by moonlight, lay the empty, darkened fields.
Reaching up, the sword-wife pressed the stick-effigy to the hardwood lintel.
"I invoke thee, Lady of Vengeance", she said, her voice low, trembling with the depth of her fury. "From beyond the veil, hear my plea. Come forth. Let justice be done."
She readied her hammer and the first of the nails.
"I name my betrayer once", she said, and spoke his name aloud. As she did so, she placed the tip of the first nail to the chest of the stick-figure. With a single strike, she hammered it in deep, pinning it to the hardwood door frame.
The sword-wife shivered. The room had become markedly colder. Or had she imagined it?
"I name him twice", she said, and she did so, hammering the second nail alongside the first.
Her gaze dropped, and she jolted in shock. A dark figure stood out in the moonlit field, a hundred yards in the distance. It was utterly motionless. Breathing quicker, the sword-wife returned her attention to the unfinished task.
"I name him thrice", she said, speaking again the name of the murderer of her husband and children, before hammering home the final nail.
An ancient spirit of vengeance stood before her, filling the doorway, and the sword-wife staggered back, gasping involuntarily.
The otherworldly being was clad in archaic armor, her flesh translucent and glowing with spectral un-light. Black Mist coiled around her like a living shroud.
With a squeal of tortured metal, the spectral figure drew forth the blackened spear protruding from her breastplate - the ancient weapon that had ended her life.
She threw it to the ground before the sword-wife. No words were spoken; there was no need. The sword-wife knew what was being offered to her - vengeance - and knew its terrible cost: her soul.
The spirit watched on, her face impassive and her eyes burning with an unrelenting cold fury, as the sword-wife picked up the treacherous weapon.
"I pledge myself to vengeance", said the sword-wife, her voice quivering. She reversed the spear, aiming the tip inward, towards her heart. "I pledge it with my blood. I pledge it with my soul."
She paused. Her husband would have pleaded for her to turn away from this path. He would have begged her not to condemn her soul with this course of action. A moment of doubt gnawed at her. The undying specter watched on.
The sword-wife's eyes narrowed as she thought of her husband lying dead, cut down by swords and axes. She thought again of her children, sprawled upon the ground, and her resolve hardened like a cold stone in her heart. Her grip tightened upon the spear.
"Help me", she implored, her decision made. "Please, help me kill him."
She rammed the spear into her chest, driving it in deep.
The sword-wife's eyes widened and she dropped to her knees. She tried to speak, but only blood bubbled from her lips.
The ghostly apparition watched her die, her expression impassive.
As the last of the lifeblood ran from her body, the shade of the sword-wife climbed to her feet. She looked down at her insubstantial hands in wonder, then at her own corpse lying dead-eyed in a growing pool of blood upon the floor. The shade's expression hardened, and a ghostly sword appeared in her hand.
An ethereal tether, little more than a wisp of light, linked the newly formed shade to the avenging spirit she had summoned. Through their bond, the sword-wife saw her differently, glimpsing the noble warrior she had been in life: tall and proud, her armor gleaming. Her posture was confident, yet without arrogance; a born leader, a born soldier. This was a commander that the sword-wife would have willingly bled for.
Behind the spirit's anger, she sensed her empathy - recognition of their shared pain of betrayal.
"Your cause is our cause", said Kalista, the Spear of Vengeance. Her voice was grave cold. "We walk the path of vengeance as one, now."
The sword-wife nodded.
With that, the avenging spirit and the shade of the sword-wife stepped into the darkness and were gone.