The Eggs near Peeper should have nothing to do with it.

This: https://i.imgur.com/N8NGxnv.png clearly states that it is about "Reaper's Cove" which is the Cave Mordus is in.

Source of this pic (warning, full of spoilers): https://imgur.com/sT8kc53

Spiegelberg! He, Spiegelberg! Die Bestie hoert nicht.