I've decided on the final elements for Ark Frontier, and with those choices nailed down I've been able to move forward on the world-building. I also started setting up a layout design for it, where I may or may not be starting to compose some of the document rather than writing it in a Google Doc like sane people do. I figured it would avoid double-handling if I just started entering creature stats directly into stat-blocks, and I may or may not decide to use InDesign like a word processor. I've done it before for PowerFrame supplements, and it does lend itself pretty well to blocking out a manuscript and then filling in the bits until it's done.
Anyway, elements! I was a little worried that ten might be too many, but they are organised into five pairs: Light and Shadow, Fire and Cold, Life and Death, Sink and Float, Spark and Null.
Some of those are pretty obvious, and some... not so much. Sink is basically gravity or an attractive force, while Float is antigravity and repulsion. Spark is electricity, and Null is sort of non-conductivity, but also encompasses stuff like anti-magic, negation, and void.
The pairs create some interesting dynamics from an in-game philosophical standpoint. Before the Phantom Storm, the indigenous people knew and utilised the five elements of Light, Fire, Life, Sink, and Spark, which they consider positive or natural forces.
The others — Shadow, Cold, Death, Float, and Null — are considered negative or unnatural; whereas normal darkness or cold is simply the absence of light or heat, the elemental forces of Shadow and Cold can actually generate darkness and cold directly. Death as a force encompasses undeath in its various forms, from animated corpses to spectres. The five unnatural forces were forbidden to mages, and even knowledge of them was suppressed. It may be that tinkering with the forbidden elements was somehow responsible for the Phantom Storm, but that's an unanswered question.
With the appearance of Phantoms (initially Shadow, Cold, and Death), knowledge of the negative elements has become widespread. Some think that they should remain forbidden territory, while others believe it is best to "know thy enemy" by researching and mastering these new fields. This has created a split between white and black mages. There are some who prefer to be called grey mages, who dabble in both sides, but most white mages would classify any use of unnatural elements as black magic.
There are also summoners, who feel that the best way to defeat the Phantoms (or to gain personal power) is to gain mastery over them and use them as tools, but this is an outlawed and persecuted pursuit.
Interestingly, this approach to the positive and negative elements also creates some conflict with the human colonists — in particular, their use of anti-gravity technology, which is seen as taboo. I suspect that the Council has placed an official ban on the use of antigrav out of respect for the indigenous beliefs, but that may not stop people from using it on occasion. The cryogenic storage system was also viewed with suspicion, but it relies on the removal of heat rather than the literal generation of "cold energy" and so it has the official seal of approval. This doesn't stop some element of prejudice against the recently-thawed Sleepers, however.
World-building is interesting because each piece you add sends ripples across the setting, interacting with already-established elements and suggesting new things to add and directions to explore. Add sufficient details and follow the consequences to their logical conclusions, and eventually a complete picture of the world emerges like a tapestry.