The Underworld Mystery

The Underworld Mystery is a clue hunt within Starlight City. With the inclusion of the Freddy's Minigame, players received hints about "Major reveals" to those who find it. This is possibly linked to Location Unknown.

The clues
There is a wall of signs at the end of Freddy's Minigame, which is in no particular order, scrambled and randomized

The signs say:

button | beneath | save | iron | trap | enters

the sewers behind | can't | them | pizzeria | door | who

will | truth | have | shown under | the | ground

An iron trapdoor WAS found behind the pizzeria, but no signs on how to activate it with a mentioned "button".

What we know
We don't have much yet, the iron trapdoor and Location Unknown are the only solid leads so far. Perhaps more will be added in the future! We know that the Sewers, which run under Starlight City are somehow connected to this.