The Reforging is the process by which the Stormcast Eternals return from death. When one of Sigmar's storm-forged warriors is slain, their soul does not pass to the underworlds; instead it streaks back to Azyr as a bolt of lightning, where the celestial smiths labour on the Anvil of Apotheosis to hammer the soul back into a living, armoured champion.
The gift has a hidden price. Souls were never meant to be unmade and remade, and each Reforging burns something away: a childhood memory, the taste of food, the warmth of an old love, sometimes an entire personality. Warriors who have died many times may return colder and stranger, more storm than person, their humanity thinning with every resurrection. This slow erosion, often called the flaw in the process, is one of the great tragedies running beneath the setting's heroic surface, and Sigmar's smiths have never fully solved it.
The Reforging is also what makes the Stormhosts a sustainable army. Because their warriors can be recovered and recast, the God-King can wage wars of reconquest that would annihilate any mortal force, though every veteran who marches out again does so having paid a toll no one else can see.