Excuse the broad question but I couldn’t resist making a metal pun.
So in my universe the Fair Folk encompass a large group of creatures. They live in their own little pocket universe, in which there is very little raw metal. Though they are all quite different, all of them share a few similarities.
- They have a roughly humanoid body plan (emphasis on roughly)
- They are not, nor have they ever been, human
- They are all capable of manipulating ambient energy/internal energy, explaining their magic.
- They are all weak to metals (not the music genre)
Some are weaker to certain types of metals than others, while some are immune to a specific metal, like a leprechaun with its gold. Each metal also causes a different effect on the fair folk which can be broadly broken down into 5 categories.
- Alkaline/alkaloids: React very strongly with Fair Folk tissue.
- Radioactive metals: Supercharge Fair Folk abilities, but rapidly kill them.
- Iron type metals: Cause direct harm (iron causes burning and disrupts powers).
- Silver type metals: Are toxic or drain energy from Fair Folk (silver is toxic)
- Lead type metals: These cause odd effects (lead causes physical weakness, tin blinds them)
Iron type metals are near its group on the periodic table, the same is true for the silver and lead types. Some metals can be two different types at once, and alloys have all the effects of their component metals, but to a lesser extent.
So with all the exposition out of the way here is the question: What could cause the alkaline and alkaloid metals to react so extremely to fair folk tissue?
P.S. I realize there is a lot of information here for this question, but I plan on linking back to it in the future, so I figured I might as well do my explaining now, rather than having to go over all this again later.