Well, I had ambitious plans for Shadesmar and the Oathgates, but I can't even get my custom entities to spawn there. Ah well.

At present, there are a couple of advantages to going to Shadesmar.

1. It provides a (relatively) safe place to build bases and such (if you can get there without being stuck in obsidian)
2. (The main one) Travel in Shadesmar is far faster than in the overworld. Each block travelled in Shadesmar is 16 blocks in the overworld. (in theory). At the very least, it's a safe place to travel atm.

Lore

Realmatic Theory

In the Cosmere, the universe in which these stories take place, everything exists in three realms. The Physical Realm, is where most people live, and where their understanding of the cosmere begins and ends. The Cognitive Realm, also called Shadesmar, is the Realm of Thought. This place is where the spren are native to, and everything in the Physical realm is reflected there, depending on how people see it. On Roshar, every object in the physical realm manifests as a small, dark bead in the cognitive realm, causing Shadesmar to appear as a great sea of beads. Large bodies of water (such as lakes and oceans) manifest as large islands or continents of obsidian, providing land on which to walk. On these expanses of glassy obsidian, the spren build their cities. Everything alive in the Physical Realm manifests as a candle flame in the cognitive. The third realm is the Spritual Realm, the place of gods. Unlike the other two, "place" does not really apply here, and this is where the bulk of the power of the gods exists.

Travelling Between Realms

Transportation

A Surgebinder with access to the Surge of Transportation can, with a little practice, move between Realms. It is much easier to move between the Physical and Cognitive than it is to enter the Spiritual, and it is easier to enter the Cognitive than to leave it, but both can be done.

Oathgates

With a little convincing, the Oathgates - ten great platforms which can be used to travel across Roshar instantly, can transfer people between the Physical and Cognitive Realms. This is the method imitated in the mod, along with Transportation.

Perpendicularities

For those without access to either of the first two methods (which is almost anyone on planets other than Roshar), the only way to travel between Realms is using a Perpendicularity. Perpendicularities are places where the power of gods gathers, usually in the form of a pool of liquid. Entering one of these can transfer a person between the Realms, but it is not always easy. This method usually only applies on planets with at least one Shard (god) investing the world (i.e. putting their attention/power into it).

Building an "Oathgate"

To craft an oathgate, first surround a diamond, emerald, or amethyst shard in the crafting grid with stone to make oathgate stone. Then, you can build this like a nether portal to create an "Oathgate". Right-click on it with an honourblade or a Radiant Blade to ignite it.