Blood sky

Players reach the realm by climbing above the Overworld, which stops at y=320, through a portal built high enough to cross the sky. Above it hangs a flesh-and-bone world lit red under a starless sky, and nothing there lives. A Heartstone and a Rift Anchor placed on the way let a player step back through the rift, and an arrival falls out of the Overworld sky, where Slow Falling catches the player.

Four countries split the realm, and each one carries its own color scheme and haze: the Crimson Expanse is covered in flesh turf laid over blood stone, the Marrow Wastes are dry and bone-white, the Ichor Basin has clotted ground with pools of blood, and the Vein Forest is dense with heartroot and short red trees. Ten structures are grown procedurally instead of stamped from saved templates, so no two are alike. The server and every player need the mod installed. It is published for Forge only, in the 1.21.11 game version, under the MIT License, which is not open source.