### One-Shot Adventure: “The Shattered Sanctum”

#### Adventure Overview
In the high-magic realm of Eldoria, a once-holy sanctuary known as the Sanctum of the Celestial Light has fallen into disarray. The Church of the Radiant Dawn, led by the esteemed Archbishop Welby, is embroiled in a scandal that has shaken the faith of its followers. Whispers of corruption and dark rituals echo through the streets, and the clergy have begun to lose confidence in their leader. The players must investigate the Sanctum, uncover the truth behind the scandal, and confront a malevolent force that threatens to plunge the realm into darkness.

#### Setting the Scene
As the players gather in the bustling city of Luminara, the air is thick with tension. Colorful banners flutter in the wind, but the vibrant atmosphere is marred by hushed conversations and wary glances. The sun hangs low in the sky, casting long shadows over the cobblestone streets. The scent of incense wafts from the nearby temple, mingling with the aroma of baked bread from a nearby vendor.

The players receive a summons from a desperate vicar, who implores them to investigate the Sanctum. He speaks of strange occurrences: flickering lights, ghostly apparitions, and a growing darkness that seems to seep from the very walls of the sanctuary.

#### Key Locations
1. **The Sanctum of the Celestial Light**: A grand cathedral adorned with stained glass windows depicting celestial beings. The once-bright interior is now dim and filled with an unsettling chill. Shadows dance along the walls, and the air is thick with the scent of decay.

2. **The Crypt of Whispers**: Beneath the Sanctum lies a labyrinthine crypt where the church’s secrets are buried. The walls are lined with ancient tomes and relics, but dark magic lingers here, twisting the very essence of the place.

3. **The Hall of Confession**: A room where clergy once offered solace to the troubled. Now, it is a place of dread, with echoes of anguished cries and flickering candles casting eerie shadows.

#### Investigation Component
As the players explore the Sanctum, they can gather clues by interacting with the environment and NPCs:

– **Clue 1**: A torn confession scroll found in the Hall of Confession reveals a vicar’s secret dealings with dark forces.
– **Clue 2**: A frightened acolyte in the crypt speaks of a hidden chamber where forbidden rituals were performed.
– **Clue 3**: A spectral figure appears, revealing that Archbishop Welby has been possessed by a malevolent spirit seeking revenge against the church.

#### Enemy Encounter
**Boss Enemy: Archbishop Welby (Possessed)**
– **Type**: Medium Undead (Possessed Human)
– **Armor Class**: 15 (Natural Armor)
– **Hit Points**: 120 (16d8 + 48)
– **Speed**: 30 ft.
– **Abilities**:
– **Strength**: 14 (+2)
– **Dexterity**: 12 (+1)
– **Constitution**: 16 (+3)
– **Intelligence**: 18 (+4)
– **Wisdom**: 20 (+5)
– **Charisma**: 22 (+6)

– **Actions**:
– **Multiattack**: The Archbishop makes two attacks with his spectral staff.
– **Spectral Staff**: Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 15 (2d10 + 4) necrotic damage.
– **Possession (Recharge 5-6)**: The Archbishop can attempt to possess a creature within 30 feet. The target must succeed on a DC 18 Wisdom saving throw or be possessed for 1 minute. The possessed creature is incapacitated and controlled by the Archbishop.

#### Conclusion
Once the players confront and defeat the possessed Archbishop Welby, the dark spirit is expelled, and the sanctum begins to heal. The players can choose to restore the sanctum to its former glory or expose the corruption within the church, leading to a potential power vacuum in Luminara.

As the sun sets, casting a golden hue over the city, the players emerge from the Sanctum, their hearts heavy with the weight of their choices. The fate of the Church of the Radiant Dawn hangs in the balance, and the echoes of their adventure will resonate throughout Eldoria for years to come.

#### DM Tips
– Encourage players to role-play their interactions with NPCs, allowing them to gather information and form alliances.
– Use sensory descriptions to enhance the atmosphere, emphasizing the contrast between the sanctum’s former glory and its current state.
– Be flexible with the investigation component, allowing players to explore different avenues and come up with creative solutions to uncover the truth.