An unpleasant event that occurred when one of two Ancient Eggs was opened.  Featured in Season 2, Chapter 1.  A gas was released, and those who breathed it in became like movie zombies, mindless and engaging in acts that spread the plague at an exponential rate.

Said zombies basically grabbed or grappled their opponents, and breathed a gas into their faces that, upon inhalation, instantly spread the condition.  Two named characters who were known victims are Jen and Diana.

What the end result of the plague would have been is unknown, as it was stopped when the other egg was opened, releasing Lucia, who somehow immediately ended the event.