The Empire does not officially condone the worship of any gods. It's not that they deny their existence, they just don't believe that they deserve to be worshiped. Like their off-shoot state, the Covenanters, they are far more likely to bargain with a given entity to reach a short-term, finite goal. This lends the Empire towards a mechanistic view of the universe where everything can be explained using pseudo-scientific principals.

The Empire does acknowledge the existence of the soul as one of the components of human beings. They also acknowledge that souls are generally indestructible and exist beyond death. They believe in transmigration of the soul from one life to the next as well. Unlike the Mithraic and Gallic Churches they do not believe in any deity-sponsored heaven or hell. They do acknowledge that dealing foolishly with demons can lead one to "sell his soul" and that if someone offers his soul to a demon in return for some favor (and doesn't get out of the bargain) that is pretty much takes said soul out of circulation. They do not believe that simply summoning or dealing with demons under other circumstances will do this.

Variations:

The official party line is that souls (and only souls) are reincarnated, and that they tend to stay within families or at least within social class. [Note: this has contributed to inbreeding -- the desire to keep souls "in the family" by giving them few other options] The exception to this is that, through emulation of the Ancestors, the Founding Fathers, who were more perfect in mind, body and soul, the common soul can attain more of that natural perfection and "move up" in the cycle (the idea of the Spirit of Man - see below - survives on in one form here). Emulating the Founding Fathers means exemplifying such ideals as duty to the state and family, discipline, wisdom, stoic fortitude in the face of hardship, etc. (The Five Virtues of the Mos Maiorum - in general, attitudes that make you a better citizen and servant of the Empire/Emperor).

Souls between reincarnations are still somehow present in the world and are aware of the doings of their decedents. They may be influenced by their perceptions and can in tern influence the material world with the power of their wills -- i.e. they can bestow a 'curse' or 'blessing' on a family, through force of will, much like the infamous "Mage's death curse" but more vague and long-term. For this reason the Imperials in particular are very careful with the dead. They have very strict rituals for dealing with them, and they fear disturbing ghosts. Raising the dead is the ultimate no-no, which is why the Necropolis has such a reputation and are so feared. See more on ghosts below.

Early on a cult started that proposed a concept of Nirvana, borrowed from the Elves/Gaels. These people believe that the soul can reach a state of perfect harmony with the world/universe and no longer is reincarnated but instead exists in a state of spiritual union with "everything." Again, this is dependant on "natural" not supernatural ideals. This is a small cult in both the Empire and Covenant states, but does exist in both. It's considered rather new-age and flaky. Long ago, there were beliefs that, rather than achieving Nirvana, one achieved a union with the Spirit of Man, which might actually accompany the reincarnated back with them to the next life, leaving them "enlightened," and able to help mankind achieve great things. This would make them the equivalent of a Mithraic saint. Note that this belief faded over 1000 years in the past. It still exists in a few rare books, but has been forgotten about by philosophers and the public.

A common belief among people of all classes is that some aspects of personality are retained through reincarnation. This leads to people taking wealth and secrets with them to the grave in the hopes of reclaiming them in a future life. It also leads to people attempting to learn about past lives in the hopes of learning where some of these treasures might be. This limits the inheritance of old family heirlooms, as many of them are buried with their owners. Grave robbing in the Empire is a fairly lucrative business, as you might imagine, but also fraught with hazards. There are stringent laws against it, as well as customary taboos. Messing with a grave can bring a curse upon you and your family, or so legend has it.

Ghosts are treated oddly in the Empire because of all of this. First of all, because of their lack of Channelers, the Imperials aren't well equipped for dealing with ghosts in the first place. Second, these are the ancestors, people you are supposed to revere, honor, emulate and most of all, not piss off. These ghosts may be present for numerous reasons -- Perhaps they left some great task undone in life, or returned because someone angered them or dishonored the family with their behavior. They may have come back because a sibling or loved one has been reborn and they were drawn to that soul. There are legends in Empire mythology of people having "guardian" souls or ghosts -- poltergeists or other spirits that seemed to follow them around for much of their lives or at least their childhoods. In general, ghosts are something to be wary and respectful of. You don't want to anger them, and it would be disrespectful to try and get rid of them per se (though finding out, if possible, if they want something done is okay). Because of this, people living in a haunted manor will treat the ghost just as if it is a living family member -- talking to it, setting a place at the table for it, cleaning its room, etc. If a ghost is particularly unnerving or unquiet the family will even abandon the entire house or possible the entire manor to it. There are places like this in the Empire, especially on the islands -- old overgrown and moldering manor houses, fully furnished and unoccupied except by the occasional family member brave enough to enter and leave some offering for his restless ancestor. Note: souls and ghosts are seen as more powerful than the living when it comes to manipulation of fate/chance/probability. They are not limited by physical bodies stuck in one place and time and are more a part of the 'great machine.'

Because no one wants to "mess up" the system of reincarnation or anger the recently deceased, funerals are quite elaborate and follow rigid customs as to how the body is to be prepared, how long it is to be displayed and in what way, how the deceased should be mourned, and so on. The customs surrounding the death of the Emperor are amazingly elaborate for several reasons: first, the death of a strong monarch is always a time of potential discontent in a state. Second, if a spirit can affect the well being of its House, then the Emperor as Paterfamilias of the Empire could certainly bestow either good or bad fortune on the Empire and no one wants it to be bad fortune. Thirdly, the Emperor is (automatically) close in mind and spirit to the Founding Fathers and may well be the reincarnation of one of them. These semi-deified beings are to be revered and act as the role-models for all of society, and anyone like them must be accorded great honors.

Finally -- on oaths in the Empire: Imperials don't swear "by God" or "the gods," by "Lugh's Blue Balls," or anything else having to do with deities. They do commonly swear "by the Ancestors" or "the Fathers" or the "Revered Fathers." They will also swear "by Fortuna," that is, by fate. Fortuna is not really a goddess. She may be personified in name, but this is allegorical or poetic, not actual. Fortuna is fate, cosmic design, luck, chance, etc. It is seen as a force like gravity or the humors, or the aether. It is not anthropomorphic in reality but can be manipulated through willpower by gods, demons and men. The Imperials would have understood Nietzsche's "Will to Power" concept, though they would have seen it in more empirical, mechanistic terms than we would. This ties in with the fact that magic, of course is real. People can manipulate the environment around them with pure force of mind/will alone, if they know how and are strong enough. One can conclude from this that mages are considered to be formidable both as living opponents and as ghosts. This contributes to the society's respect for mages and magical power, especially high magic (i.e. ritual). It also leads them to see those with magical power as more bound up with fate/destiny and this is perhaps one of the State's justifications for the Necropolis snatching children with potential -- " it was destined, we're just doing what is right."