Religion will be for more than roleplaying; each Power has a shrine in the Sigil Underground. Each shrine is all NPK, as is the entirety of the Sigil Underground. The shrines have a standard design, to permit easy navigation. Approximately 150 rooms, the followers of the shrine's Power can use shortcuts to traverse through the shrine easily, while everyone else is forced to wind their way through twisty, long passages. Built-in weapons and traps allow the followers of the shrine's Power to repel invaders.
At designated, periodic times, shrines will be subject to attack by members of competing religions. Each shrine has 4 emblematic control points, such as a giant salamander or a void demon. These 4 control points start out in the possession of the religion whose shrine they are in, but they may be corrupted by the presence of members of other religions. each control point has 250 integrity; every tick, for every member of a competing religion in that control point's room, one point of integrity is gained by that religion, and all other religions lose one integrity for that point. members of the control point's native religion cause the control point to regain integrity at a rate of 3 points per tick. a control point's integrity is not changed when combat is occurring in its room. when a competing religion reduces a control point's integrity to 0, that control point is lost.
At the end of the duration during which shrines are attackable, a tally of which religions were able to maintain their control points and conquer the control points of other factions is made. For every control point a given religion took over, they earn 1 Power Standing for their religion; for every control point lost, they lose 1 Power Standing.
Having a good Power Standing is useful for unlocking powerful new religion-based spells. Each religion has 3 special, religion-only spells. Each spell has a certain Power Standing requirement that must be met in order for it to be used. examples include Megalith, a Maradas utility spell that blocks an exit with a monolith for a few ticks or until it is dug through, and Magnetic Field, Vandyne's defensive armor spell that passively pulls off opponents' armor during battle.
Religion will be open to players of all levels, and non-archon players will have special roles in attacking and defending shrines. There are traps and NPCs to assist in shrine combat, but PK is the driving force behind the dynamic. To roughly balance out the distribution of followers among religions, there will be a dynamic to divide each religions' spells' power by the number of followers relative to the number of other religions' followers.
tl, dr: A new religion command will be added. You can follow gods. making your god powerful will confer religion-based spells. players of the same religion have a shrine that they defend, and attack other religions' shrines at certain times. conquering other religions' shrines unlocks more powerful religion-based spells.