After Samiel left the Qririth with Yvriane and Nefertari, they went to a safe distance, from which he planned to carry out the ritual to create Eldritch Spawns. When they were in the safe distance, Samiel singled Yvraine to stop, as he was going to activate the ritual.
This concrete ritual, fortunately, didn't require any kind of chant because the chant itself was already engraved in R'Lyehian on each of the Wardstones, so the only thing which was left to Samiel was to activate the enormous city-sized Magic Circle.
Samiel looked around as he took out a small box-shaped magetech device, which was specifically designed by the Hall of Kadath to cast something which was called "Shroud" on the entire area to prevent anyone from seeing what was happening in there.