The Hammerite Prayer Book is a text that can be found in St. Vale's library, in the mission "Return to the Cathedral". It contains the Prayer of Consecration, which must be read during a ritual to free Brother Murus.
The Prayer of Consecration
O Master Builder! We ask Thee to bless our brother who hath died in Thy
service. Forgive him the transgressions of his living days, and look with favor on
his works in Thy name.
Plumb and plane, fire and forge, purify his spirit and draw
from him all which does not meet Thy plan. Take him to serve with Thee in Thy Home
where he may rest in peace eternal.