The above is my clumsy rendition of a diagram I drew in my notebook yesterday, while discussing Divers with a fellow game designer. The upper row's your character's stats; don't know if they'll change too much. At this point they're little more than rough categories for the various ways I'm thinking of quantifying your character. Same goes for the bottom- it's a rough description for the different kinds of gameplay I have in mind at the moment. The arrows indicate that the former plays a notable part in improving your performance for the latter; so your skills help you while trying to analyze and understand the character of a region's depths, and the insight that provides can then help you while operating on the surface.
The original diagram had one other element I didn't bother to include here: A set of arrows leading from each of the gameplay types down to "Player's Goals", with a question mark next to each one. Divers is a very flexible premise, both in terms of story and gameplay. Those I've talked to so far have described a wide variety of games they'd like to run and stories they'd like to tell in this setting (one of them has actually started writing out anecdotes). These different ideas have been a huge help, often showing me new takes on the premise that I'd never thought to consider. (If you're reading this and have some ideas of your own for what could show up in a Divers game, tell me! I'd hate to miss a chance to support something you hope to see/do.
That goes double for gameplay. Here's what I'm referring to with those four phrases in the lower section of that image:
Exploration is just the task of going as deep as you can. This important because you have to "train" at the deepest levels you can reach in order to get most of your benefits for 'leveling up'. I don't think there's gonna be much die rolling involved, at least directly; you'd typically just declare that your character's diving to a certain depth. But this changes as you go deeper- the wildlife is more powerful, and you have more reasons to figure out the 'passage' across each border you encounter. Eventually this becomes mandatory. I've got no firm mechanics in mind yet, but here's about how I see it breaking down:
-First 25% of your hypothetical maximum depth: Borders are nothing, you won't even notice them if you aren't paying attention. Partial submersion and full submersion are both possible.
-26%-50%: Borders are 'speed bumps', requiring little effort to cross. Partial submersion gets trickier; this leg is where you start having to either focus your attention on your actions on the surface or those in the depths. Towards the end of this leg this means having to hold still and do nothing on one end so as to remain active on the other.
-51%-75%: Borders are 'hills'. You actually have to roll dice so as to force your way past, and each 'hill' and 'speed bump' you already forced your way over makes the next one more difficult. Full submersion is your only option.
-76%-100%: This is the point where it becomes impossible to force your way past a border even if you haven't already forced your way past a single one. The only way to get through is by figuring out the conditions to pass.
Combat is the supernatural action. It can be the primary focus of a campaign, or come up intermittently via intense clashes that occurs within the framework of a larger story. I intend to support this via two interchangeable sets of rules, with the default option being the one that handles combat (and the character's corresponding abilities) in a much more in-depth, crunch-heavy fashion. The system's adaptability could be taken a good deal further, I'll cross that bridge when I come to it.
Investigation means all manner of reconnaissance and research you can do about any given region of the depths, from getting the "lay of the land" to determining just what secrets a given element implies and what corresponding person/place/community it's implying them about. Figuring out the mechanics here is going to be an interesting matter in and of itself.
Surface Matters refers to everything that transpires while not in the Depths. While there's certainly much a diver can (an often must) do here to accomplish their goals, the mechanics will tend to be more simple and arbitrary- operating through the depths generally leaves less to chance and involves more lenient personal consequences for failure.
At this point I can name one other part of the game experience that might warrant its own group of mechanics & whatnot: modifying the depths & everything that's in them (though obviously not all at once). This could just mean using your Combat abilities to subdue something and relying on your Investigation abilities to know what you want to change & how to change it; but I could certainly go beyond that. It would be a nice way of expanding on Aura powers, to have then also be tools for influencing the Depths in various hands-on ways...
As always, thoughts/feedback/suggestions are very much welcome.