| The subject of this article has no official name.|
It is a fan-given name as substitute for lack thereof, and should not be considered as part of the Attack on Titan universe.
The Reiss Chapel was a church in a village near the Reiss family estate. Above ground, it appeared to be a simple chapel where the Reiss family would come to pray, but below the surface, it served as the site where the succession ritual for the Founding Titan took place.
The Reiss Chapel was a small church to the east of Orvud District. Above ground, it looked and functioned like any other church. Below the altar, hidden by a rug, was a stairway that led to a large underground cavern. The cavern was created by the First King, and contained hardened crystal walls that produced their own natural illumination.
The cavern below the chapel was created over a hundred years ago by the First King. Some time afterward, the chapel was built above it.
Throughout the last century, the Reiss family would gather inside the cavern in order to pass down the power of the Founding Titan every thirteen years. This was done through a succession ceremony where the current wielder would be chained upon an altar. Another family member would inject themselves with a serum and transform into a mindless Titan so they could devour their predecessor. Afterward, the successor of the Founding Titan would inherit the memories of the Fritz family and become bound by the First King's will.
Shortly after the breach of Wall Maria, the entire Reiss family gathers in the chapel. Grisha Yeager finds his way down to the cavern beneath the chapel and begs Frieda Reiss to use the Founding Titan to save the lives of the people of the Walls. However, she refuses and Grisha destroys the chapel when he kills Frieda for her Titan and proceeds to slaughter the rest of the Reiss family. Only Rod Reiss escapes his family's massacre and he covers up the truth by claiming that the chapel was destroyed by bandits in an attempt to avoid suspicion.
Shortly after the resolution of the Wall Rose invasion, Rod Reiss has Kenny Ackerman's Anti-Personnel Control Squad kidnap his illegitimate daughter, Historia Reiss, and Eren Yeager. They are taken to the cavern beneath the chapel and Eren is chained in preparation for the inheritance of his Titan powers.
Hange Zoë learns about the chapel from a report commissioned by Erwin Smith. Doubting the veracity of the bandit cover story, Hange believes that Rod Reiss is hiding something there, and has Levi Ackerman and the remaining members of the Special Operations Squad ride to the chapel in search of the captives. After finding the passage to the cavern beneath the chapter, the Survey Corps members ambush the Anti-Personnel Control Squad guarding the area. Despite the MPs' advantage in numbers, the Survey Corps manage to drive back their opponents.
Rod attempts to coerce Historia into using a Titan injection and consuming Eren, regaining the Founding Titan for the Reiss family, who are the only ones who can fully use it. Though initially receptive towards her father, Historia reconsiders upon remembering Ymir's words to her about living her own life. She breaks the injection vial before throwing her father to the floor. As she begins unlocking Eren's chains, Rod Reiss licks the remnants of the Titan serum and transforms into a massive 120-meter abnormal Titan that collapses the cave on itself.
Seeing the explosion from Rod's transformation, the Special Operations Squad moves further into the cave to find Eren and Historia. They help free Eren from his chains, but cannot locate a safe exit due to the falling debris. Finding a bottle from Rod's bag labeled "Armor," Eren decides to believe in himself and ingests the serum. After transforming into a Titan, he hardens his Titan body, leaving a stone shell and pillar-like structures that prevent the cave from collapsing further. Squad Levi is then able to secure an exit from the cave.
All remaining members of the Anti-Personnel Control Squad are killed in the collapse, save for Kenny Ackerman, who manages to survive, albeit fatally wounded.
After Historia is crowed queen of the new Royal Government, the shining stones are taken from the cavern beneath the chapel and distributed to the population to provide a limitless source of light. With this, manufacturing is able to proceed both day and night, allowing for jumps in productivity.
- An altar exists in Marley which is similar to the one found in the cavern beneath the chapel. There, members of the Warrior Unit would inherit the power of the Titans in a succession ritual resembling the one performed by the Reiss family in Paradis Island.