Greetings from Gehenna

Good day and greetings from the last place on Earth, or should I say Gehenna. Just imagine this world as it is, but war tore it apart, leaving just one country remaining. Then a wall rose up on the outskirts to keep all those vermin out and all the citizens of Gehenna in their place. Maybe the vermin got in anyhow or found a hole to sneak in through and now walk the streets, looking just like thei...