Aether

[Wolfandre]

Of course....if it is radioactive and functions like that.....are we equipping ourselves with the equivalent of uranium and plutonium? O.o

Soooooort of. Aether is funny in that your own personal wells of aether can affect your surroundings, albeit in very minute ways. We see this with spiritbonding gear, where gear is so transfused with your own aether that it can turn into a crystallized version of itself. The materia goblin in Central Thanalan actually implies that these items hit a critical point of aether overflow that they convert themselves into materia, though I think SE gave us the choice to convert so we don't just automatically lose gear at 100% spiritbond. This crystalline manifestation of personal aether can then be infused with (and removed from) other items through melding. Think of materia as personal crystals/shard/clusters, though they are arguably less pure due to being a by-product of a by-product (crystals as a result of aether run-off from a source that is, itself, a form of aether run-off from the Lifestream).

The other way you can see this is through Aetherial gear. Gear that has been worn, used, and abused, and, more importantly, bonded to its owner through spiritbonding. However, these items are such that they haven't hit the point of conversion when they were suddenly cut off from their source of aether (their owners died). That aether then does sort of the same thing materia does, in that it continued to enrich the item is was infused with of its own accord. That is why we see stat increases on Aetherial gear over what we normally see, similar to materia, which does the same thing.

There may be other game aspects that we can attribute to personal aether, such as light/full party stat bonuses (aether resonating with other, similarly strong sources) or even the Echo (seeing as it is evidenced that two individuals [unnamed for main scenario spoiler purposes] are noted, or implied, as being aether-friendly).

This brings up an interesting point in that those who do not possess strong aether wells are likely incapable of spiritbonding gear. Namely, most ordinary citizens of Eorzea. It seems materia and Aetherial gear is actually kind of rare. Now I'm wondering how strong aether/anima pools come about in a person. Is it hereditary? Random occurrence? Divine intervention? Maybe environmental exposure....hmmm....