The common things that can be done with an aspect are:
- Invoke it spending a fate point (or by free invocations sometimes) for a +2 or reroll.
- Hostile Invocation.
- Permission. Sometimes, an extra requires just a narrative justification that is allowed by an Aspect. For example, if you want to learn the Spellcasting skill in a low-magic game, you need an Aspect that simply justifies why you have access to magic. The aspect doesn't pay for the magic (you are paying with a skill slot), it just justifies narratively. This aspect can still be invoked or compelled as normal.
- Always True. It is easy to understand in situational aspects, such as Grapple which means that the creature can't move even if not Invoked. This is a bit complex because depending on how you word an Aspect when Creating an Advantage, it might have weaker or more powerful "passive" effects, which the GM must evaluate. It becomes more complex with Character Aspects because it could give a mechanical advantage to someone that cleverly worded it. An Aspect can give you permission to do something without a roll while another person would normally make a roll, or to do something with a roll while another person would normally be unable to attempt it.
However, there is something that is perturbing me. It is what motivated me to make this question.
I was reading Making Magic with Stress and it suggests using a stress track for mana. You obviously require an Aspect as permission. However, when determining the length of the track, there is one option: "Aspect-based" which seems to allow an aspect to do something more than what I previously mentioned. This allows you to have one or more Aspects that each increase the stress track length by one stress box. It is based on the Wealth Stress Track. This is quite weird because these Aspects would be more powerful than any other aspect as they also increase one of your stress tracks (If I understand correctly, these aspects can still be invoked and compelled as normal, in addition to the stress benefit).
In the Lock and Load Using Ammo Fate, it suggests that if you use an Ammo Track and use an Overcome action with Resources and succeed with style, you get the Extra Ammo aspect (same with Create Advantage) that can be Invoked, destroying it at no Fate Point cost to clear out the Ammo Track on one gun (the Ammo Aspects rules also mention Aspects that are destroyed when invoked, which can be used in addition of the normal +2 or reroll, or to make an AoE attack).
The Special Gear extra mentions Gear that can have Aspects that can be invoked or compelled as normal, but also that you can give them special flavour invocations, one-time, stunt-like bonus.
- Beyond the basic Invoke, Hostil Invoke, Compel and Always True, what more things can do an Aspect?
- Why in the Mana or Wealth examples an Aspect is allowed to increase a stress track? Is there any "cost" for those special Aspects that I'm missing? For example, in the Mana stress track, not all players necessary must be spellcasters. That means that if I want both players (spellcaster and non-spellcaster) to be balanced, the spellcaster must pay each of their magical benefits with a cost (for example, Magic Skill spends a Skill slot), so if there are Aspects that increase your Mana stress track, what are they using to pay the cost? (I don't think that an "Aspect slot" could be an answer if that Aspect is still allowed to be Invoked and Compelled as normal).
An answer such as "Do what the GM wants" or "If the party feels appropriate allow it" is not helpful.