Magic

Magic is finite.

The importance of gold
Gold is the most common magical catalyst, being required for nearly all spells, and is ubiquitous in the world as a source of magical power.

Other natural sources of magic exist, however, the most common of which are pearls formed in a magic-storing gland known as an aurum, present in all creatures with innate magic power. Druids and rangers in particular are known to hunt magical creatures for their aura instead of relying on gold mined from the earth.

Magic also exists in low concentrations within the atmosphere, and such power can be drawn upon by skilled magic users for casting cantrips.

Cantrips are spells that are designed to be very efficient, being able to be cast with only the ambient mana within the air, but are very difficult for the average caster to master, with most mages being only able to perform a handful of them. Sorcerers and warlocks can ignore the gold cost of spells.

Sorcery is a sign of prestige and power in noble bloodlines, and sorcerer families go to great lengths to keep their bloodlines pure. Owing to a sorcerer's ability to cast without the use of gold, sorcery is highly prestigious.

Warlocks can also cast without the need for gold, which tempts many an aspiring mage into making a pact. Unlike sorcerers, however, warlocks enjoy no prestige for their status, and are actively shunned or even hunted for making dangerous pacts with what are commonly seen as malevolent and unpredictable beings. As a result, warlocks typically keep the source of their powers a secret, or else seclude themselves from polite society to escape judgement.