Dungeons & Dragons players have long ignored material components, because they have very little impact on play. Casting fireball? Do you have some bat guano in your pack? (“Yeah, yeah, yeah, I bought plenty of bat guano in town. [eyeroll]”)

It was traditionally a way to put limitations on spellcasters or to at least make them do a bit of role-playing to find material components, but hardly anyone ever bothered. However, there’s a simple way to make material components matter without making them a bookkeeping nightmare.

Felstone Powder

Felstone powder is my term for a magical element found in mineral form that is used by spellcasters to power their spells. Every spell requires some, and it costs money (or is found in lieu of treasure). Specifically, it costs 10 gp of felstone powder per level of spell. So a 3rd-level spell costs 30 gp’s worth of felstone powder.

If a spell requires some specific material component that has a specified value, that cost is in addition to the felstone powder cost. So, an 8th-level spell that requires a 1000 gp diamond would cost 1080 gp in materials to cast.

Essentially, this is a way to make spellcasters spend money in order to cast spells. They only need to track their treasure as usual and mention buying some amount of felstone in places they visit (or taking it off the smoking corpse of a spell-slinging opponent).

This is especially useful in relieving druids of excess cash, since they don’t have much reason to build a stronghold. (Altho I recommend encouraging druids to buy up land to keep as a nature preserve where they can conduct their druidic rites.)

Lifestyle

If you assess lifestyle costs between adventures (which you should), wizards and clerics should have to pay double. This accounts for the felstone powder they expend when using their spells between adventures.

If 10 gp just to cast a 1st-level spell seems excessive, don’t just change it to 1 gp. That would just be an annoyance. Instead, say felstone powder is covered by the character’s regular lifestyle costs, but they have to buy expensive arcane tomes to level up: 1d6 per level x 100gp.

Acquisition

As DM, you can decide how rare felstone powder is. Is it available in every town? Or do spellcasters have to get it from a city?

And you can set the price. It just needs to be high enough to be worth tracking the costs of casting spells, or else it’s pointless.

Variations

You can also decide want to call it. Instead of “felstone”, you might call it mythril, adamantite, wolfram, etherstone, or some such thing.