House of Illusions is an event in the Stories of Tamriel that takes place in Skyrim at 4E 203.
A strange house has appeared outside Whiterun. It appeared overnight. Every night odd sounds are heard from the house. Jarl Balgruuf sent some guards to investigate...they never returned. Whiterun Hold is now known for the deadly house and people are advised to avoid the house whenever possible.
A group of adventurers has decided to investigate the mysterious house outside of Whiterun. As they enter, they encounter many startling illusions. Erys, one of the adventurers, eventually encounters an blood-starved vampire named Sorik, who had been trapped by the Dawnguard in the same house for an hundred years with a silver sword and the illusions created through the influence of his starvation.
After Erys and the party release him from the house, they return to Whiterun to claim their reward, but John Smith, one of the adventurers, learns the dark truth about Sorik and that the spirits of the ones who died by his hands wants justice exacted upon him.
The party decide to visit the Hall of the Dead to consult with a Priest of Arkay and find Sorik, but they all pass out. After another illusive dream, they wake up in the real world, at a room in the Midden at the College of Winterhold.
Erys meets a man by the name of Ganlian Adaire and the latter explains that the party was used as test subjects for an new type of spell. To save the others, The former volunteers to link her mind with the other party members with the help of the latter. Erys began to explore the multiple realities and confront Sorik in the 'alternate world'. The former promises to kill the latter before leaving the alternate world and returning to the real world.
After speculating that Sorik may be residing in Cyrodiil, Ganlian had a Khajiit assistant named Dar'nabil accompany her to Cyrodiil and as a guide and bodyguard. Back at the College, one of the adventurers, a man by the name of Cloud, follows Erys's trail towards Cyrodiil with a horse.
The three later arrive at Bruma and started searching in Chorrol next after coming up empty in the latter city. After some time, a courier warns Erys about "The Advisor" before leaving immediately. The party searches in the Imperial City next and beats an group of Vampires that ambushes them. They rest in the city for the night before visiting the Arcane University for answers.
After yet another fruitless search, they decide to return to Winterhold and make a stop in Whiterun. They later find out that the 'house' was real. With the help of a mage named Verus, they decode that the house is empty.
They later head for Dragonsreach and find that Sorik has enthralled everyone in the castle and intends to kill Jarl Balgruuf for being buried under his own house years ago when the Dawnguard tricked him into revealing his vampirism. Erys manages to kill Sorik with a well-aimed shot with a bound bow and free everyone enthralled from control. After explaining the situation to everyone in the castle, they head back to the College in Winterhold.
With Sorik out of the picture, Ganlian asks the heroes to test the full version of his illusion spell one more time, secretly much to the chagrin of Erys. They later arrive in an illusory world, and with the advice of the former, manages to complete the spell and test it by training against illusions.
After some time, Erys manages to escape, but her friends remain trapped in the dream world. Out of a sudden Cloud and one of the adventurers are trapped by a rogue Verus. After escaping, they find out that Sorik's conscience still lives within Verus, and Ganlian suggests an idea to force him out. Using a soul trap to capture Verus in Ganlian's black soul gem, they succeed in destroying him and ending the chase.
Before Cloud left, Erys handed him a unique ribbon as a token of appreciation before the former left and the latter checking on her friends.