Chaplains were originally formed by [[Lorgar]] as part of the religious slant he brought to the [[Word Bearers]], charging them with spreading the cult of the Lectitio Divinatus, his early form of [[God-Emperor of Mankind|Emperor]]-worship. After assuming control of the Council of [[Terra]], [[Malcador the Sigillite]] instructed the Space Marine Legions to employ Chaplains to enforce the [[Council of Nikaea|Decree of Nikaea]], the Emperor's restrictions on [[Librarians]], as a sort of proto-[[Commissar]].
[[File:DreadnoughtChaplain01.jpg|300px|thumb|left|This Chaplain is a Dreadnought, [[Chaos Space Marines|your]] [[Heresy|argument]] is invalid]]
In the present, a Chaplain's role in the chapter is primarily ensuring the spiritual purity of the chapter: rooting out potential heresy, instilling and enforcing the wisdom of the [[Imperial Cult]] (although given the high amount of autonomy the Astartes gets, they may or may not have their own interpretations), and reminding his brothers of the chapter's traditions and history, from which they may draw strength and inspiration.
In battle however, Chaplains are just as inspiring, as they are in a chapel sermon. Donning black power or terminator armor with a skull helmet, a rosarius, their badge of office (a sacred power maul called a "Crozius Arcanum") and a fiery rhetoric able to inspire the most unmotivated troops into fanatical warriors of the Emperor on the spot. A chaplain maintains the morale of his battle brothers, ensuring their [[RAGE|righteous anger]] is stoked into a raging fire, even in the most bleak and darkest of battles, either through inspiring sermons and/or being an example of The Emperor's fury by bashing His enemies into a bloody pulp with extreme prejudice. Outside of the company Chaplains, you have the Master of Sanctity or High Chaplain oversees the [[Space Marine Chapter|Chapter]] Chaplaincy and is a senior advisor to the [[Chapter Master]], and the Reclusiarch, who oversees the Reclusiam, where the Chapter's sacred relics and trophies are displayed. Many Chapters combine the two posts, but not always.