The Well of Souls is an an ancient well-like stone structure found in the hidden catacombs beneath the fabled House of Pekara in Earthrealm. It made its appearance in one of the loading screens of Mortal Kombat: Deadly Alliance and was first mentioned in Kenshi's story in the Krypt of Mortal Kombat: Deadly Alliance as well.
The Well of Souls is a stone well that served as an altar to house a certain sword that is the final resting place for the spirits of forgotten and great monarchs with fighting skills and swordmanship known only as the Warrior Kings. It laid undisturbed within the tomb of the Warrior Kings for centuries.
When the young swordsman Kenshi opened this well, he had freed the souls trapped inside. Unable to deal with the horror that was released, he was left forever blinded and those souls turned out to be the spirits of his forgotten ancestors, the Warrior Kings before they were consumed by the cruel sorcerer Shang Tsung who deceived their descendant Kenshi into committing this act of sacrilege.
In Mortal Kombat 11, the Well of Souls is referenced again. It is said to house souls for Shang Tsung to consume. It is revealed that Kronika seeks out the souls so that she can use the temporal energy housed within them to create her New Era. Jackson Briggs and his daughter Jacqui Briggs are sent to intercept Kronika's retrieval, but they are thwarted by Cetrion.