Firmus

Often stocky and stalwart, Firmus Resonants tend to be patient and practical, they make for great teachers and reliable friends. Whilst they can be stubborn and a bit too serious, they are driven to persevere through troubles.

Firmus, one of the five forms of Resonance, is the ability to manipulate solid matter. The density of said matter is one of a few determining factors for how difficult it is to manipulate using this power.
Whilst a rarer power than Atmos and Fluxus Resonance, due to its difficulty, Firmus Resonants have found many uses for their powers.

Warfare

In warfare, Firmus Resonants had a myriad of uses; from constructing barriers, trenches and traps, to more offensive uses such as hurling projectiles, impaling their foes on sharp rock and in some cases, crushing armour or bone. Firmus Resonants could also simply weaken armour by stretching it out, causing it to become thinner and more easily defeated.
Depending on its speed, these Resonants can also stop projectiles in mid-air and redirect them back at its origin or towards another hostile target. Should the projectile be too quick to slow down in time or simply require too much energy to do so, a Firmus Resonant might opt instead to realign their armour - if they happen to be wearing any. Doing so might take the form of completely removing any armour from their back and instead shifting all of the metal in front of the Resonant in a wedge shape to cause a deflection.
Alternatively in historical hand-to-hand combat, they could simply rotate the rings on chainmail armour in an area, if for only but a moment - like bunching up a net, to make it significantly harder to penetrate or break.

Utility

Historically, this ability was used in industry to increase efficiencies in quarrying, mining, and metal-work. For Firmus Resonants are able to cleanly remove chunks of material from the desired areas increasing worker safety, as well as efficiency of transporting waste.
Additionally, there are accounts of once famous figures who used Firmus Resonance in masonry, sculpting and architecture to further their craft, pushing materials to their structural limits.
Some ingenious Firmus Resonants even found their fortune in prospecting for rare minerals and metals, by pinging bodies of water for gold and then tracing the origins of said gold. They would then remove the soil and rock, leaving only the precious resources behind which could then be carved, carried and carted away.

Puzzle locks

In order to secure wealth and protect secret passage-ways, Firmus Resonants have been known to create massive doors with no keys or handles, seamlessly embedded into walls and floors alike. By manipulating the mechanisms within the door, hidden from sight, it is possible for a Firmus Resonant to unlock the otherwise unopenable lock.

Metal-Bender Worker by Emma Haephrati