Artifacts

Artifacts. Some people invest their soul's strength into objects along the lines of a theme. This can manifest as technology that should not be (Metal Maiden's suit has rocket boots built in... but her suit flies far better than simple thrust can explain and for far longer than any fuel supply that fits in with her could provide), magic items (like a flying carpet or a stick that grows and shrinks on command), crystals, or similar. The artifacts are actually powered by the user: The artificer sets a pattern into the object, applies power, and gets an effect out.

Like spell slingers, an artificer is very flexible: It is possible to design an artifact (or set of artifacts) to do almost anything. However, an artificer has two big downsides:

The first is time. An artificer must spend time investing their power into their artifacts, and plan ahead for what effects they need. In an unexpected situation, an artificer is in trouble.

The second is that their power is external: Metal Maiden needs materials to make her suit, and needs her suit with her to fly. Break her suit and deny her any opportunities to rebuild, and she's effectively powerless.