Zombie World
The Entrance of the Zombie World you will find North-East Corner of Bank in Lost City.
In this World you can earn Souls to buy stuff from Vendor stones. (Flying ships, Private Vendors and their time)
Zombie World is in a Parallel world that means you cant recall, sacred journey or gate travel out. You need to run all the way back.
The Exit is behind the entrance North-West Corner where the fire is.
In the Zombie Word you will find Grim Reapers and some infected (Rotting Corpses) monsters.
If you die there you will become an infected monster that has all your uninsured stuff.
Grim Reapers are hard to kill i suggest you group up to kill Grim Reapers.
If you sucessfully killed a Grim Reaper he will spawn a chest on ground which you can pick up.
Inside the chest you will find some Souls, Badges, Gold or a Steed of the Grim Reaper (Etheral Steed).