Guiltythree
This is just a theory, but I believe this is the moment Sunny had previously killed Nephis, Cassie was too late to stop him, and thus Sunny became permanently crazy until he rewound himself at the source. SoS wasn't just talking about Wind Flower timeloop when he said "i've lost count at this point."
This has to be how Nephis dies. Sunny in his maddness turns on everyone including a weakened and unsuspecting Nephis. The mad prince didn’t go mad because of the defilement or due to Nephis death. Something happened where he needed to use the crowns ability then proceeded to kill that thing and then Nephis.