Severus side-alonged them to a remote room in the dungeons. As the three of them arrived by one wall, sigils painted all over all four walls came to life, lighting the space in a flickering glow. A triple circle - iron filings, ground cinnabar and salt - was drawn in the centre of the floor.
"If you would step inside," Snape murmured to Lily, indicating the circle with a sweeping wave of one arm as he drew his wand with the other, "I can begin."