The following blurb is to be included at the end of the character concepts section of advanced character creation:
It's important to keep your concept in mind when selecting the abilities in the following steps. In particular, you should look at what an ability does mechanically. Most abilities also have a non-mechanical description or "fluff" that explains what you're actually doing in the context of the setting. While the mechanical information describes things like healing hitpoints or dealing extra damage, the fluff describes things like "twisting gyres of energy" or "ancient written magic of the dwarves". However these are not binding. You can replace these with any other in-universe explanation that you and your GM agree fits. Some options may even have suggested alternate fluff. This, like the default fluff, is intended to provide you with ideas and is in no way binding.

The following are sidebars that should appear near the option listed. These are just a couple of things that I thought could use it or that somebody specifically requested I write one of these for; there's certainly potential to have alternate fluff sidebars for almost anything.

Tactical Insight track: Note that this track is also great to represent traditional bardic skills. Perhaps your knowledge comes not from tomes and study, but from stories and songs. This kind of knowledge may be less accurate in many settings, but for the sake of game mechanics it can function identically. As a bard, you may fluff abilities as bardic songs and tales that you regale your party with in the heat of battle.

Path of Rage track: The Path of Rage track is designed to represent berserkers and people who exceed their natural abilities through severe emotion. But this doesn't have to be purely rage. Greek myths have similar tales of powerful emotion, and this track can represent a frenzy fueled by the tragedy of a slain family, as Kratos and Hercules, or the joy of slaughter, as with the followers of Pan and Dionysus. It can also be entirely non-emotional in nature. Perhaps your character transforms into a beast-like thing, unlike any mortal, whether that's because he's a werewolf or because you call upon the primal spirit of the wilderness as a conscious action. It could also represent a demonic pact, with your patron aiding you in battle, but taking a bit of your life and leaving you exhausted afterwards. Any reason you can think of to be more physically powerful for a short while fits this path well.

Virtue: The Seven Circles of Renewal track: The Virtue track gives you the ability to create generic "fonts". While that's all well and good from a mechanical perspective, for your character they could be much more. Does your character serve a diety? Perhaps each font is a small shrine, formed of your god's benevolence and your will. Does your character follow a darker path? Perhaps you scatter a few drops of the last blood squeezed from an enemy's heart, and the residual vitality is directed by your will to your allies. Do you have allies amond the fey? Perhaps you summon fairies or redcaps to aid your fellows with their magics.

Mechanist Savant track: The Mechanist Savant track is made with the Hallow setting in mind. If you're using a different setting, some aspects of this fluff may not fit well. That's fine, you can always refluff it. Instead of creating mechanical things, perhaps you have access to fae magic, and you create sprites or fetishes that do your bidding. Perhaps you're a summoner, and you pull imps and mephits from the depths of hades to serve your will.

The Earth Cracks feat: Does the Broken Earth exist in your setting? If it doesn't, you can still use the Earth Cracks feat. Consider where else your character might get this power. Perhaps the Earth herself has taken a liking to you. Perhaps the character is simply an earthly being, tied to the firmament. Perhaps his tremorsense is entirely non-magica, merely a skill picked up as a tracker or an ability his bloodline accesses naturally.

The Sun Grows Dim feat: If the Brass dawn doesn't exist in your world, the Sun Grows Dim feat needs refluffing before you can use it. Perhaps you craft things out of shadow because you're a handyman who spent a century in the darkness above the stars. Perhaps you use something other than your shadow, such as a bit of the stuff from which the gods made the world. Perhaps you don't actually create anything, but you reach across space and time to take it from elsewhere.