Regulus

The mercury being extended an arm that elongated unnaturally, pointing at Arthur.

Arthur's hand instinctively moved to his weapon, but the being made no aggressive moves.

"Before you proceed, you must be tested. The unworthy cannot look upon Regulus."

With that declaration, the courtyard began to change. The floor cracked and shifted, pieces rising to form a labyrinth that assembled itself before their eyes.

"Complete the Labyrinth," the mercury being instructed. "Reach the center, and you may proceed to the inner sanctum."

The being began to dissolve, its form losing cohesion, mercury-like substance dripping into nothingness until no trace remained.

Arthur found himself teleported directly into the heart of the maze. Walls towered on all sides, their glossy surfaces reflecting distorted images of himself. The ground beneath his feet pulsed with faint blue light, marking pathways that appeared and disappeared seemingly at random.