Read more about Caldera on my Obsidian Portal website.
The core rules explain that disenchanting a magic item extracts the magic from it and transforms that magic into a fine, silvery dust called residuum. It’s so rare and useful that a mere pound of it is worth 500 thousand gold pieces. Wow, right?
In Caldera, residuum is not so rare. In fact, the magical energies pool in the rock below the city, whose citizens mine the stuff. Well, they don’t mine pure residuum; they’re mining ore, called arcanite, which contains minute quantities of residuum. They use heat and magical processes to smelt the arcanite, and to extract the residuum. The miners are exposed to all kinds of strange magical effects over time, and most exhibit strange transformations. In general, the process the smelters use protects them better (through use of shielding, special suits and goggles, and so on).
Residuum comes in many forms. The most common form is called arcane residuum, and is a fine, silvery powder that shimmers with moving colors. In Caldera, it’s worth about 100 gold pieces an ounce (about 1/300th the value of what the core rules describe). There are other forms, each with special magical properties sought by wizards and enchanters.
Magic in powder form is incredibly useful to one who knows how to use it. However, the street has discovered a simple use: snorting it. When ingested or snorted, residuum produces heightened emotions in the user. In the right headspace, the drug creates incredible euphoria or megalomaniacal confidence. Unfortunately, these feelings are addictive and over time a residuum dependence requires more and more of the drug to achieve the effect. Withdrawal symptoms are painful and often lead to death (or suicide). An ounce of residuum will cover a typical addict for a few weeks. In addition to magnifying emotions, taking residuum occasionally transforms users permanently, giving them strange magical powers often accompanied by changes in physical appearance. These powers are often dangerous, making encounters with angry or scared residuum addicts potentially lethal.
There’s an even purer form of residuum called liquum. When residuum is combined with elemental water, heated with elemental fire, filtered through elemental earth, and then distilled with elemental air, the result is a shimmering liquid form of magic a thousand times more potent than residuum. It is generally too expensive to be used as a street drug, but it is used in powerful enchantment rituals as an amplifier.
A knowledgeable arcanist can use specially-prepared residuum and liquum to boost the power of his spells. This works like the metamagic feats from the previous rules edition, making saves more difficult, damage higher, range further, casting easier, and so on.
In general, because of the presence of mineable residuum in Caldera, magic items are more common. In fact, there’s an industry built around enchantment. The most common magic sold is for convenience (lighting, cleaning, cooking, communication), safety (weapons, security), or entertainment (games, recording and playback).