Obelisk of Light was an ancient relic that was one of many keys to other worlds, including the world to the Great Old Ones. The Priest's mission was to reclaim it.
It was once held in Rome by the Pope Benedixt XIV, but had to move it to the new World due to the rumours of the artefact despite the vows of silence on his followers. 
It was put in the deepest mines of Lorwich by the Vatican. In 1972, the Vatican Priests and the Martense Order witches joined forces, unofficially, to create a rift in the earth to seal the obelisk.