My son has a rich imagination centered around two flying dolphins. Usually, they swim around the sea taking to the air to visit other friends in faraway places. Some of these faraway places are "Kansas", "Mexico", "Ice Cream Land", "Pie Land", and "Different Water".
Not wanting to miss out on his multi-verse hopping, delphine adventures, I asked him about some of these far away places. He described Ice Cream Land as a place that was made entirely of ice cream. Ice cream people lived there. Ice cream dolphins and sharks lived there, too.
Before I get too far, yes, I asked about "Different Water". He said that is was like the ocean, but in a different place. That's all I got. He's five, so I'll cut him a break for now.
In any case, I pondered what would creatures of Ice cream land be called? They're like elementals, but not composed of a single element (unless you consider ice cream an element). I wanted a name that would represent their composition of the fundamental 'stuff' to be represented. So, I happened upon primordials and the name has stuck so far.
The spark my son's imagination provided was to imagine a multiverse without the Ptolemaic/Wu Xing elemental planes. What if the other planes were made of various complex compounds, but were just different?
In addition to pondering these planes, I happened upon a note for an adventure seed about summoning a fire elemental that broke free of the summoners' control. I wanted these new planes to have creatures composed of fire, but how would that work?
First, how would a fire-creature survive? There needs to be a source of oxygen. Instead of breathing, though, it should get oxygen by eating something. Searching the interwebs, I found sodium chlorate, a key component in some chemical oxygen generators. Skipping down to a wikipedia entry on Oxygen Candles, I figured that these fire creatures could make these candles to eat. The fantastic element I needed to add was a plant native to that plane that contains lots of sodium chlorate. Assuming that existed, these Fire Primordials could make food with this plant and iron filings. When ingested, it would produce oxygen for about six hours. Better yet, their digestive tract has naturally occurring iron, so that they only need to ingest this plant.
So now, I have shemped the fire elemental, plus I have an exotic plant that could be used as more adventure seeds.
Let's add in some more twists. The Fire Primordial wouldn't have access to this plant while it is in our world, so it would have to know enough to heat up salt water and somehow pass electricity through it. So, I figure that this creature should be intelligent. Given that Andras now has a system that allows just about anyone to cast a cantrip level spell once a day (with about a 50-50 chance of success), I figured that his 'spell' would be just enough to deliver a short electrical charge. The spell has no value in combat.
Then I formed a picture in my head of this Fire Primordial sitting in a cave with a large stone mug filled with salt water. He heats the water (he is made of fire) and casts his cantrip. Now he has a "tea" of sodium chlorate to drink. I also figure that he doesn't need to eat as much because our world has more oxygen in the atmosphere than his own.
If you're still with me, let's add one more item to the mix. Do you know what happens when you mix sodium chlorate and sugar? Big explosion. So this Fire Primordial can be killed by ingesting sugar. In other words, sugar is a poison to him. I can imagine a couple of beet farmers keeping the creature at bay by throwing beets at it. In some ways, it appeals to my sense that ordinary people should have a way to fight off a creature like this, even if it has a low chance of success.
Now to finish the adventure tentatively entitled "Escape of the Fire Primordial". In the meantime, I need to think of a name for the plane of his origin. Eldur? Gasira? Nar? Fy-Heem?