Description
Things Betwixt
This mod adds a new feature: interdimensional teleportation through falling into the Void of a dimension.
Usage
When a player is falling below Y= -20, they are instantly teleported into specified dimension in the same X- and Z-Coordinates but a specified Y-Coordinate. This data is to be specified and or changed in configuration. Directions on how to use these parameters are described in config parameters' description.
Default Y - [ 256 ]
From Overworld - [ -1 ] - to the Nether
From Nether - [ 1 ] - to the End
From End - [ 0 ] - to the Overworld
Configuration
There are also 5 slots with similar parameters for custom teleportation links in Configuration, which can be edited via Minecraft Mods menu or directly through the config file. (Works with modded dimensions. The only problem is dimension ID 100, don't use that) Furthermore, both the 3 main dimensions' links and the mod itself can be deactivated in the configuration too.
The Void
Though this mod makes it possible to travel through dimensions via the Void, it is STILL under a layer of unbreakable bedrock, so mods adding possible solutions to this problem are highly recommended to use along with Things Betwixt.

