Your challenge rings out across the cliffs like shattering crystal. The Voidwalker's nebulous form contracts sharply, their edges becoming more defined as if your words gave them sudden substance. Where there was only star-flecked darkness now stands a tall figure wrapped in robes that drink in the torchlight, their face hidden beneath a cowl of swirling cosmic dust.

'Proof?' The Voidwalker's voice emerges as a chorus of whispers from between worlds. They raise one hand and unmake a standing stone with a gesture - the ancient monolith dissolving into strands of blue-black energy that dance between their fingers before reforming perfectly. 'The void is patient. The void rebuilds. What more proof could ephemeral flesh require?'

The Moonweaver hisses like steam on cold iron while the Sunforged Knight's armor creaks with the strain of withheld violence. Above you all, the aurora-born fourth figure begins circling like a predatory bird, its form occasionally resolving into something with too many wings.

Suddenly, the Voidwalker lunges forward, their hand passing through your chest without resistance. Your breath catches as visions flood your mind - the birth and death of galaxies, civilizations rising from stellar ash, your own face reflected in a hundred dying stars. When they withdraw, you're left trembling with cosmic vertigo, your ceremonial robes now threaded with veins of pulsating void-stuff.

'The real question,' the Voidwalker murmurs as the unstable ground shifts beneath you, 'is whether you can prove yourself worthy of our guidance.'