A Ser Killian Adventure
Spoiler Alert - The following adventure is based on the D&D adventure Dragon of Icespire Peak. You may not want to read this if you plan to play that adventure.
Approaching the Tower
After a journey of about a day from Leilon, our party of heroes approaches the Tower of Storms. The tower sits upon a craggy island connected to the mainland by a narrow causeway that barely rises above sea level.
Traversing the causeway (1), they get attacked by 6 sahuagin. Our heroes dispatch the enemy in short order.
Note: I added some encounters and changed others to improve the adventure for solo play.
Next (2), a giant crab erupts from the sea and attacks Haiden. Haiden's spear finds a soft spot in the crab's carapace, wounding it. But the crab's claws snap onto Haiden's arm, drawing blood. The others come to assist, but their attacks glance harmlessly off the crab's armored shell. Finally, Killian lands a mighty blow that cleaves the shell and kills the crab.
They reach the island and begin to ascend the craggy slopes (3). They find a small cave. When Nashad peers in, a ghostly presence reaches out and possesses him.
"Before you take hasty actions, hear my tale!" the possessed fighter pleads. He explains how the unholy priest of the tower killed him and trapped his soul on earth. The spirit could not be freed until the priest was truly dead.
Agreeing to undertake the spirit's quest, the party continues toward the tower. As they approach its gate (4), a swarm of harpies attack. Their song charms Alyn and Nashad so Killian and Haiden must fight alone. Nevertheless, our heroes drive off the beasts.
The Tower
They enter the tower (5). A trap drops a stone on Alyn, who suffers an injury. They pass through a room (6) without incident and enter the back room (7). There, they meet the priest.
The priest unleashes a bolt of lightning, which strikes Killian in the chest and knocks him to the floor. Alyn rushes forward, and strikes a telling blow on the priest. Growling with anger, the priest lashes out at Alyn, drawing blood. Nashad enters the fray and scores another hit.
The priest attacks Nashad but Killian recovers and counters. The paladin's blade bites deep. The priest turns on him and drives him back with a series of attacks. He is about to strike when a sword suddenly pierces him from behind. The priest stares at the blade sticking through his heart.
The priest coughs and gasps, "you win today, but this is not over. My master will revive me...." With this he collapses.
The priest is dead but the tower's evil still pervades the place.
"We must destroy the root of this evil," Killian proclaims.
They continue up the tower, defeating a few cultists on one floor (8) before coming to the top. There, they see a heart lying upon a pedestal. The heart is beating and an eldritch light emanates from it.
"This is the source of the evil! We must destroy it!" commands Killian.
Nashad rushes forward. He swings his two-handed battle axe at the heart but a ray of light zaps him. Killian dodges another ray and stabs the heart. Nashad attacks again, this time slashing the heart. Finally, Haiden attacks. His strike splits the heart in twain. Then, the heart erupts with a burst of magical energy, knocking our heroes flat.
Aftermath
The spirit thanks the heroes for freeing him. He then releases Nashad from possession.
Victorious, our heroes return to Phandalin without further incident. They can now prepare their assault on Axeholm.