Ethersparks

"I wasn't too sure whether or not to put this under spells or conditions, so I put it under "spells"
To put it simply, "Sparkers" are walking Ether Fonts. They can provide a steady supply of Ether passively just by being near someone and they are very rare. A Sparkers birth is entirely random, and Ethersparks manifest at a random point in time too, unless you are a Witch, in which chase you are always born with an Etherspark. Ethersparks aren't particularly powerful by themselves, a lot of Sparkers can't perform magic, but in the hands (or heart, rather) of a Witch or any practitioner of magic, they suddenly become living weapons, despite only being able to cast 1 or 2 types of spells. Maybe 3 if they are a trained Witch.
P.S. All Witches are Sparkers, but not all Sparkers are Witches. I see Sparkers get ridiculed and shunned just for simply being a living battery, don't just assault them."

Effect

"Ethersparks provide a steady and endless amount of Ether to the user and those around them, allowing them to cast spells freely, if properly trained (though they rarely are). Having an Etherspark is very useful for Elves, they won't need Moonkings to survive beyond fonts and could support another Elf on their journeys. Sadly, despite being able to form within Dragons, they simply aren't enough to sustain them. They still went extinct."

Manifestation

"Due to the fact that Ether is practically invisible when exposed to air or not actively being expelled from fonts, the slow trickle of Ether from a person is literally unnoticeable unless you're an Elf."

Source

"Sparkers are named as such because of the glowing blue crystals embedded in their rib cage. Usually, it's the size of a small paint pot, the kind you buy to paint model kits with. But very rarely do we see larger Ethersparks, usually signifying a relatively powerful mage, able to cast 4 or 5 different spells."

Discovery

"There weren't any records of Ethersparks existing before the Waning age, which suggests that Ethersparks somehow manifested in an age when Ether was scarce. They were discovered when a surgeon was cutting open a human who needed a heart transplant and discovered a glowing blue shard of Ether embedded near his rotting, black heart. It was emitting Ether so the doctor had to remove it and study it, but when it left the body, the Etherspark crumbled in his hands and ceased to exist. The patient recovered after transplant and when questioned about the spark, he simply said that "I don't know what you're talking about, but I feel a little emptier inside now." Later it was discovered that, Ethersparks don't cause heart disease, it was just a coincidence.
It is important to note that it is indeed possible to extract a Spark and not have it crumble. Very rarely, an Eclipse Cultist church will have sparks kept in small vials stored somewhere "sacred"." "There is no secret technique to how we extracted them, we just got our hands on a lot of Sparkers and purged those heretics of their sin. We keep the particularly abhorrent sins that didn't crumble in used vials, to serve as warnings and teach our students what to find in a heretic." -High Eclipse Priest Juza before his execution.

Applied Restriction

"Sparkers tend to not know they're Sparkers unless they live near/are Elves or is born a Witch. They don't really have the opportunity to learn spells because the only ones that can use magic are either a cackling Witch who aren't always nice, or a studying mage, which are incredibly rare. And even then, there is no guarantee that you will be able to cast the same spells as they know/teach. You either have to be a Witch to know how to cast magic, or incredibly lucky to cast it by accident, and then recreate it again."