Living strength
Gigants are enormous non-magical mortals whose raw physical power can accomplish work that other peoples would reserve for siege engines or large crews. Their affinity with stone is explicitly not a spell. It is a physical intuition for weight, faults and the behaviour of rock, paired with the strength to move boulders, cut tunnels and reshape fortifications by direct labour.
Their scale naturally shapes their architecture, warfare and relationship with the landscape. In a world where supernatural power often defines authority, Gigants demonstrate a different kind of exceptional capability: patient endurance and physical force so great that a single body can alter structures and terrain without magical assistance.