Generally, the afterlife is thought of as another realm where the spirits of the dead (and sometimes their physical bodies) go after death. However, that is not the only realm that may exist outside the mortal one. Some religions have other realms where not-quite-human/mortal creatures live.
There are two major components when creating an afterlife or other realms of existence for your religion. First, what do people believe exist? Second, what actually exists? The following questions can be utilized for both questions. And, this being Fantasy, the next question is: how can magic manipulate these other realms?
Helping people manage death is seen as one of the main components of a religion. If the afterlife people believe in doesn’t give them comfort about death, it is entirely possible people will come up with an addition or alternative that will comfort them about death.
So, what happens after people die? There are a variety of options you could choose from.
- Pleasant afterlife realm/paradise
- Bleak/nothing afterlife realm
- Punishment realm/hell
- A continuation of normal life
- Union with deity
- Guardian spirits
If a pleasant afterlife is promised, what form does it take? What do people think of as paradise? Is there a golden city? Untouched wilderness? A picturesque pastoral existence? Does paradise vary per person, or is there a unified vision throughout the religion? If there is a unified vision of paradise, are any deviations from the standard allowed, or are they treated as heresy?
Is paradise allowed for all people, or is it specific to certain individuals? Is anyone guaranteed entry into paradise? If so, can their entry be revoked? For people who are not guaranteed entry, can entry be earned? What actions are required? How do those actions relate to the values, virtues, and taboos from previously?
Are there multiple pleasant afterlife realms a person could go to depending on their actions in life or devotion to particular deities? Think of the division of dead between Freya and Odin in the Old Norse religion.
If paradise is not the automatic result for your average good person, where does the average person go? For a number of religions, there may be a large realm of what is essentially nothing where the majority of shades remain. This could also be a temporary area where souls are judged before being sent to one afterlife or another.
Punishment is another very common component of afterlife. Sometimes there is a punishment realm where all or some souls might go permanently or for a limited amount of time. Other times, specific well-known offenders (perhaps from mythology or history) will explicitly be called out for punishment. If someone is being specifically punished, than it is highly likely that the punishment will be unique either to their crime or to the person in particular. (Consider Tantalus being tempted by both food and water after serving his own family to the gods.)
Punishment, like paradise, can consist of multiple realms as well. Offenders might be divided by offense, or length of time needed in the punishment realms. Or, they can even divided by which deity they’ve offended, and be personally punished by that deity (or its minions).
The ways the punishment realms are described will related to what the originating culture found unpleasant or deadly. Hot, dry cultures could have deadly heat in the punishment realm. Cold climates might have an unending winter.
The afterlife might not be anything special, especially for your average person. It could well be that the afterlife is seen as a continuation of a person’s daily life. In this case, grave goods (if they are provided) will likely be things that people used in their everyday life.
On the opposite spectrum, afterlife could mean a union with (a) deity, either basking in their presence or actually merging with them. The afterlife could also mean ascension to godhood, especially for rulers, demigods, or those who have done great deeds (as your protagonists likely have).
Then again, dying might not mean a person’s spirit goes to any other realm at all. A person could stick around, either as a ghost causing mischief or as a protective guardian spirit. If you have a form of ancestor veneration in your culture, this might actually be the most logical afterlife.
Alternatively, the person’s soul could be reincarnated. They could be born again in another animal or person, either immediately or sometime after death.
Another option that does not deal with an actual afterlife is that nothing happens at all. When people die, their existence ends. There’s nothing left of them. This could work well if it is what actually happens to your people, in contrast with an elaborate religious practice. Or, this could work with an atheist society that cares little about the afterlife.
If there is magic in your society, how does it relate to the dead and the afterlife? Classically, necromancy was a form of divination that relied on asking more knowledgeable spirits for information. Recently, necromancy has been portrayed as raising the dead (in one form or another). If there is necromancy in your world, what form does it take?
- Incorporeal spirits/ghosts
- Banshees (depending on your mythology)
- Mindless zombies
- Sentient zombies tend to fall closer to the lich category of undead
- Wights (depending on your mythology)
Does necromancy remove a soul from the afterlife? If so, it is likely a related skill to summoning. Does it simply manipulate dead bodies? If so, it is likely a related skill to healing or compulsion magic. Is it a blend of both?
What do the religions of the world make of necromancy? Is it a skill that is sacred to the church, and heresy for anyone else to use? Is necromancy restricted to the followers/priests of certain deities? Is it utterly banned as a perversion?
If necromancy is allowed in your world, what practical forms does it take? Can the testimony of the dead be used in legal trials? Is necrophilia still illegal, or does it not count if someone’s consciousness has been raised and they can consent? Can marriage continue after death is someone is raised? Can a living person marry a dead person? What happens to inheritance and property rights if life can continue after death? Can the dead be used as messengers or spies? Can they be captured and used as power sources?
What other realms exist in your cosmology other than afterlife realms? Do particular mythological or fantasy species have their own designated realm the way that humans do?
Many portal fantasy stories go back and forth between Earth (our world) and Fairy/Faerie/the Other World/etc (the magic world). What is the cosmological connection between them? What if there are more realms than just the two?
As an example, consider the multiple realms of Norse mythology. There were two realms for the gods, since there were two different tribes of gods. Two different realms for elves, and another for dwarves. A human realm, a giant realm, and others.
Or, you could simply go with a multiverse option. There are different realities, yes, but each reality has its own planet and solar system and continents and a wide variety of cultures (and religions!) that your person could end up in (or summon from).
If you have other realms of existence where creatures live and your world has magic with the ability to summon creatures to a person’s aid, are the creatures coming from a person’s actual realm, another realm of existence, or are they being created on the spot? Do mages think it’s one when it’s actually another?
What do the summoned creatures think of the human mages summoning them? If they’re of animal intelligence, their emotions will be fairly basic and likely ruled by fear and the spell compulsion. If they’re intelligent and self-aware, their reactions may be more mixed. Do they resent being pulled from their lives in to this strange other world? Do they like the chance to explore some place new? Do they pretend to cooperate just to lash out at the first opportunity? Do they meekly obey so they can spy on humans and report back home when the summoning wears off? Are the leaders of their race considering a war against the humans for kidnapping their people?
Or maybe the physical creature isn’t taken into the human realm, and just their spirit is. In that case, what happens to the body left behind? It could slip unconscious or die or fall into a deep sickness. Think of the ancient practice of shamans calling souls back to their body when someone falls ill. Perhaps there are rival groups of shamans who bring souls back and summoners who steal them away.