Mafia 33. The American Dream

Fits the "kingdom of green faces":
1) Vervolka:
Faction for Heroes 3:
Swamp (Reptiles)
2) Kitz Kitsunka for the same reason.
3) Mold: "Shake heretics, shake mutants," Marcus wouldn't approve, but you get the idea.
4) Rimpa has a greenish face in his avatar.

I don't know what fits "Stone" or "you can say whatever you want."

"Ribbon" on which the "secret journey" takes place
1) Neyra has a "secret."
2) Nebko loves to travel to parallel worlds.

I can't think of anything else.

Perhaps, Vissi was the killer. At least, something somewhat similar in meaning is in his signature.

Where is it?

"offspring of the kingdom of green faces" - whatever the faction, Sylvan with 5...) profile of Nebo)

Lol, what? Sylvan with green faces? I'm not even going to mention that two snails are being linked to two different murders and Nebko.