Halfway Thoughts -
A creature (most likely greek in origin) that requires sacrifice every 7 years. Sounds like it walks on 2 legs but makes an animal-like sniffing sound. The park is a maze - minotaur? But invisible? Maybe it's only visible to the people who can be consumed.
Atrius (like Atreus, king of Mycenae, another Greek reference) used his paint like Theseus used thread to find his way to the temple.
The remaining survivors could kill the creature, if it is a minotaur.
