the story of Assassin's Tale follows Frisk as they attempt to join or infiltrate the Mt. Ebbott Brotherhood of Assassins who are rumored to have magical powers and the Key to immortality.
A long time ago before the first Crusades a Viking warchief, Aegir, was sailing along the cost of present day America with his warband when they stopped in the bays of what is now New York. These vikings were on the trail of an ancient legend that told of a magical 3 pronged spear that would grant any who touched it immortality. The trail stopped at the entrance to a large mountain and as the vikings journeyed the walls become metallic and strange lights glowed from the walls. They entered a large cavern with large pools of lava, swampy marshes and snowy tundras before they found a large and solid door. Try as they might their strongest warrior could'nt break it down but when Aegir placed his hand upon the door it swung open revealing ruins of the First Civilization leading to the fabled 3 pronged spear.
Upon touching the spear Aegir saw a vision of Thor , or a First Civilzationer with that name, who warned Aegir specfically about the end of the world to come thousands of years into the future and of the Assassins would save the world. Thor granted Aegir with power over the 3 pronged spears gift of immortallity, but at a cost, when he emerged from the vision his body had been transformed into a large goat monster. Although initally terrified of Aegir's transformation his warband soon bowed before who they dubbed 'The King of all Monsters'. Aegir found what was known as the first Brotherhood of Assassins and set up his Sanctuary in the caverns of Mt. Ebbott.
In modern times the Mt. Ebbot Brotherhood remains as one of the largest Assassin cells still active, all be it entirely made up of hundreds of monsters, due to it's magical barriers preventing none Assassins from being able to find the entrance. Aegir, who's name was corrupted over time into Asgore, is still the just ruler and mentor of the monsters. But a splinter group led by his former Queen Talia, who's name was corrupted into Toriel, threatens to up turn the secrecy of the Mt. Ebbott Brotherhood.
This is when Frisk enters the Story ,as the first human Assassin to step foot in Mt. Ebbott in almost 100 years they become a crucial player in the fight between The Traditionalists and The New Dawners.
Unified Route: Bring peace between the factions
Serve in the Shadows Route: Help Mentor Asgore quell the uprising of the New Dawners
Protect the Light Route: Help Toriel Lead Monster Kind above ground to reveal themselves the humans for better or worse
Monster Route: Destory the Mt. Ebbott Brotherhood
Aegir/ Asgore: The Immortal King and Mentor of The Mt. Ebbott Brotherhood. He is a fair and kind ruler even though he values traditional ways over progression.
Talia/Toriel: Former Queen and Magic Mentor of the Mt. Ebbott Brotherhood , current leader of the radical splinter group the New Dawners.
Undyne: Master Assassin and head of The King's Eyes, an elite assassin team tasked with long recon outside Mt. Ebbot. She is gruff and loud but can be quiet as a whisper.
Wing Ding Gaster: Master Alchemist and current royal scientist alongside Alphys. He is extremely solemn and all business, but always manages to smiles around his children.
Sans: Novice Assassin, Older brother of Papyrus and son of W.D. Gaster. Largely lazy and apathetic he works hard in assassin's training to protect his brother, he blames himself for Papyrus losing his arm.
Papyrus: Footpad Assassin, younger brother of Sans and son of W.D. Gaster. Kind-hearted and full of spirit, despite being very kind he places the codes of the Brotherhood over his own guilt. He lost his left arm during a botched assassination mission.