So, I said this:
It does strike me that Demon might serve as an interesting template for variations on the same theme, of spirits in mortal bodies. You could semi-easily do something more generic by assuming a kind of animist setting, and allowing characters to host animal, plant, rock, river, sky and so on spirits. This would immediately tackle the issue that most of the demonic powers aren't very demonic. Some of the others could be discarded, or turned into generic Lores accessible to anyone - although personally I'd want to drop or pare-and-merge some of them for being either incoherent or rubbish. Again, that seems like it would fit well with the idea of Generic Supernatural Power that spirits might be able to bestow on top of their specific spheres of power.
Money, meet mouth.
Reality is composed of two worlds: the tangible and the spiritual. Entities that are unassuming to our eyes may represent enormous spiritual power. Storms and lakes are physical manifestations of nature spirits, and fire spirits glimmer amidst the flames. Old, learned animals grow powerful in the spirit world, and some can pass between the two. Items valued by mortals, or used for generations, wax fat with spiritual power until their consciousness stirs. Few mortals can perceive the influence of the spirits, but they are everywhere, largely taking no interest in mortal affairs. Most are too weak to be detected by even the most sensitive mind.
At times and in places where reality is thin and the boundaries blur between the worlds, spirits may cross over to our world. Many are mindless or disinterested, some hostile, a rare few benevolent - and some are curious. Unable to travel the mortal world as freely as they wish, these latter spirits seek out humans with compatible souls. Maybe desperate, maybe curious, maybe frustrated, hungry, ambitious, naive, eager; whatever the spirit finds appealing. They find such souls at a fateful moment, most usually the precious moment between life and death when the boundaries blur - and they offer a bargain. I will help you. I will lend you my power, my knowledge, my magic. Take me with you.
Those who accept become Vessels, mortal hosts to powerful spirits, sharing their bodies with alien minds.
Merge with ancient and mysterious entities! Gain supernatural powers! Meet strange people and, let's be honest, set them on fire and steal all their stuff on the orders of people whose instructions you're following for reasons that are never entirely clear!
Just like in Demon, there are a stack of abilities and stuff. I don't particularly feel the urge to mess with them.
Lores are broadly divided into Common Lores and Aspect Lores. The former can be taken by any character without additional cost. You select three Aspect Lores when creating your Spirit, which represent the most prominent spiritual aspects of the entity: these are equivalent to House Lores. Other Aspect Lores count as out-of-House and are more expensive to train.
Although I'd use the existing Lores as a basis, honestly I think they need enough examination that it's not worth including them in this post. Stuff like Faith and Torment would also need reexamining.
The point of the game
Unlike Demon, I'd like there to be some more inbuilt assumptions about what you actually do, which means a vague kind of metaplot/assumed goals that we can hang actual play on. Ideally, and mostly out of contrast with most games, I'd like this to be something that is mostly both player-driven and proactive, but it's not that easy to build both into a game.
Broadly speaking, I think I'd like to set this up as a situation a bit more like a spy story, or the kind of fantasy where you're setting off to overthrow the Dark Lord rather than survive long enough for the plot device to kick in. So, rather than the PCs getting on with their lives and waiting for stuff to happen to them (be that random encounters or receiving missions), this would be a setup where there's a known large-scale situation that the PCs are aiming to change in their own favour. This would also create some sense of a natural endpoint. The players, rather than the GM, would make a lot of the decisions about what kind of stuff was going to happen in the next scenario, and this would typically be about the PCs doing something, rather than responding to NPC actions (although NPCs should still be doing stuff).
I think I'd also assume a much looser social setup than is generally the case in White Wolfy games. Rather than official cliques where the PCs are bit-players answerable to a host of superiors, I'm imagining a setup a bit more like... I dunno, school. Or, again, quite a lot of fantasy. PCs share ideologies and aims with some NPCs, but there's no formal structure in which they could be promoted or punished. Messing up is going to tick people off, and potentially alienate people, but you can't get busted down to private and the only way to impose a punishment on you is forcing you to take it. Your alliances might shift along with your interests and character development. If you want to go off and attempt some grand and risky plan, it's on your own head.
I think if you're aiming to get PCs to be more active than reactive, they need to have a few things.
One is information: it's a problem being active in many games because neither PCs nor players actually know what there is out there that they could be doing. You can do very sandboxy stuff where you wander around exploring and doing known types of things (looting dungeons, slaying bandits, trading with aliens, winning tournaments) without much information, so if you have fairly generic goals like "get rich and famous" or "learn stuff" you're okay. On the other hand, neither you nor your character can work towards a long-term goal of rooting out White Circle Clan influence in the Middle Kingdoms, destroying the Eleven Scrolls of Zaar and sending the demon Gharnakl back to hell that your eternally-reincarnated spirit may finally rest, unless you know that all of those things exist.
Similarly, to have a meaningful proactive goal of eradicating traitors within the Adeptus Mechanicus on Hurvin III, the group has to agree that there will be a fair number of traitors on Hurvin III, and that the character can actively work to discover their existence, track them down, reveal or attack them, and that the fallout from their actions will be acceptable. Warhammer 40K actually makes that relatively simple, because the setting establishes clearly that heresy is everywhere and rooting it out is a laudable goal - you don't need to define this as an aspect of your specific game. So I think to a significant extent, this is a case of articulating what kinds of things there are that might be done, either directly or by virtue of a strongly-presented setting.
The other main one is autonomy. It's hard for characters to take an active hand in what's going on if they canonically lack authority, rights or power. Characters in any kind of sociopolitical genre may be heavily restrained by their superiors: you really don't want an MI6 agent breaking into the Kremlin without a really good reason and authorisation, because of the potential fallout. You don't want military operatives taking unauthorised action that might destabilise a political situation, or throw off a planned large-scale operation by changing the enemy's plans, or lead to a counter-attack when your own side isn't yet ready for a battle. A lot of games with strong social setups have PCs as minor players (at least early on), and they are heavily subject to the permission of powerful NPCs. They may not be able to make decisions or deals, and may be excluded from important information. They may be unable to call on the resources needed to achieve a reasonable goal, or to access relevant people and places.
Rights are a similar issue: if your characters are socially weak, then it's hard to be the protagonists. Serfs can't easily carry out an investigation into a lord who can kill any of them on a whim, let alone for snooping in his private business. Lowly employees will struggle to make political plays if at any time they can be ordered to do whatever they're told and have any arguments, however good, dismissed out of hand. Members of a despised minority without legal protection will have real trouble working their way to seats on the Planetary Council, if they're constantly at risk of being randomly arrested, beaten and have no entitlement to jobs or fair treatment.
And power is important because you need it to do stuff. There are different kinds of power, and in most games you gain power as you go along. Power might be as simple as a skill, or it might be political influence, or the ability to cast fireball. A character who can't really achieve things under their own steam isn't able to take action towards their own ends, but has to rely on other people doing things for them. There's only a small subset of genres where such a person can be a protagonist, and few of them would make for interesting games.
The most straightforward premise seems like it would be a strong two-world split. There's a spirit world where spirits of all kinds get on with stuff, having only minimal or indirect involvement with the mortal world. Even things like an animal spirit isn't the soul of a specific animal.
Let's also assume that there are some serious internal politics going on in the spirit world, and one of the issues at hand is their relationship with the mortal world. Specifically, how directly they are allowed to interfere with the mortal world.
A significant number of spirits have ventured into the mortal world, which contravenes the philosophy of the PC spirits. Depending on the political setup chosen for the spirit world:
- there may be an official agreement which has been broken by some splinter group that disagrees with it;
- the spirit world may be a fairly amenable place, and a malevolent faction is seeking to gain control of mortal world affairs as part of a plot to Rule The World;
- the spirit world may be a dangerous place full of spirits hostile to humanity, and a benevolent faction may seek to aid mortals through subtle manipulation or even public disclosure;
- a whole gang of spirits may have gone joyriding in the mortal world, be they fool kids, a misguided cult, or even a cynical business offering illegal adventures - in any case there is a link between them and a hierarchy;
- individuals may have wandered through independently at various times;
- a research project might have sent spirits through who have now gone rogue;
- the whole thing may be above-board, but some spirits can't handle mortality, becoming addicted or unstable over time - these must be retrieved for treatment or imprisonment;
The PCs aim to merge with a mortal host long enough to capture, persuade, recruit or destroy the invading spirits. This will tend to involve learning to use their powers in the mortal world, learning to cope in the mortal world, tracking down the spirits and working their way through a list or up a power structure as they neutralise them.
They are likely to face both pressure and support from their own faction, and hostility from the invader faction, but are mostly independent operators.
Some specific event has occurred which drives the PCs to enter the mortal world, seeking something there. Other spirits also reside their for their own purposes.
- A way to end a threat to the spirit world, such as to destroy the Sauron-equivalent or retrieve a lost item that provides magical balance
- Mortal activities are affecting the spirit world, and subtle intervention is needed. They must realign certain sacred sites, unblock magical flows disrupted by mining, replenish damaged forests and so on.
- The journey itself, and certain conditions attached, are the purpose. The PCs must succeed in order to settle a bet, win a point of honour, prove their family wrong, make a political point or otherwise triumph over spirit-world rivals. Think Around The World In Eighty Days
The PCs aim to merge with a host in order to travel around and perform the activities they planned. This will tend to involve learning to use their powers in the mortal world, learning to cope in the mortal world, researching and seeking out the important places or things they quest for, and confronting any mortal or spirit that opposes their activities.
In this setup, it's unlikely PCs have very much support available. They may prefer a subtle and stealthy approach to avoid attention, or their allies may be dealing with the threat elsewhere. This is not a very faction-based game.
The PCs' main purpose is to explore the mortal world and learn to understand it.
- PCs are themselves the faction that wants to have fun in the mortal world. Other spirits disapprove and try to interfere, hunting them down; these might be political rivals, family members, or even officially-sanctioned assassins. To deal with the situation, PCs must learn to survive and thrive in the mortal world, and turn its resources to their own ends.
- Hopping into a mortal body is a fairly common activity, but there are squabbling groups of joyriders with different loyalties. PCs are essentially part of a gang, and devise semi-arbitrary activities that either prove the valour of their gang (in a prestige-themed game), build the practical power of their gang (in a more political or military game), or harm the interests of others.
- There's no particular harm in riding mortals, but some spirits just can't take it. The PCs have intrinsic drives to, essentially, have a jolly holiday in the mortal world, but will occasionally run into unstable and dangerous spirits, or spirits that weren't really sentient to begin with. This is a very sandboxy approach, and players will need to be fairly interested in roleplaying learning to be a mortal, or showing off by pulling superhero stunts, or visiting cool real-life locations, or some such agreed focus.
- The PCs are essentially scholars or scientists, aiming to learn to understand and manipulate the mortal world. This would be more along the lines of a certain strand of C20th sci-fi, with the focus on what it's like for the characters to encounter certain things (some of them dangerous or strange) and deal with humanity while maintaining their guises.