The universe in which Lythbound takes place is collectively known as "Lyth." It is a mechanically-infinite selection of realms which are interconnected (some, more tenuous than others). Those who reside here are physical creatures, who teleport and travel around to realms for various reasons.
Storylines for Lythbound will typically focus on specific realms where Lythians have gathered. For example, there may be marketplaces where travelers can gather and shop, knowing that a variety of shopkeepers will always be set up. However, individual storylines are open and allow for travel in places which may never be mentioned in "canon" lore if so desired.
Many of Lyth's realms are inundated with magic, though some may prefer to rely on technological advances in their day-to-day life.
Adult Lythians who have received training may create their own "Sanctuary" spaces, which are small "pocket realms" that can be controlled and changed at will by the individual creator. These Sanctuary realms function somewhat differently from other realms, as their access can more easily be restricted from visitors, and the creator is in full control.
Lyth is full of a myriad of creatures which are collectively known as "Lythians." Those who are considered playable characters all have sentience, intelligence, and reasoning abilities which could be equated to human-level. However, there are also many beings which exist that are more animal-like. Some of these are dangerous, and must be protected against while in the wild; others are domesticated and kept as animal-esque companions or like simple pets.
There are some beings throughout the realms who exceed what playable characters are capable of, as well. Some of these beings make their presence known on a regular basis, while others are only known through stories and myths.
Communication between language-capable species is relatively straightforward. Within realms and species, individual written and spoken languages may exist, but inter-realm communication is possible via a form of common communication magic. With the aid of thoughts, feelings, and impressions, communication is typically clear, so language-related misunderstandings rarely happen between species that commonly interact.
To move around between Lyth's realms, most individuals use something colloquially known as a "Door." Doors are essentially a method of teleportation which can be used to travel between known realms.
Summoning a Door can be done anywhere (into thin air!), and creates a literal, physical door (or similarly-shaped creation that can be walked through) which is unique to the individual in design. Focusing on the destination and stepping through the Door allows the summoner to teleport to their desired location. Some realms require "Keys" in order to more easily access them. Keys are items that are important to the realm in some way, and act as a type of "focus" that help direct the teleportation process.
This method of teleportation is a type of magic which all Lythians innately have and learn to nourish as they grow into adulthood, though there may be uncommon exceptions where they do not possess this ability. However, it can still be exhausting, and takes energy to summon a Door! They are primarily used for inter-realm travel, but may be used within the same realm. However, the energy expenditure is often not worth it within the same plane, unless traveling a very long distance (or not requiring that energy for other things).
Teleportation via Door can be very imprecise; the more familiar the Door's summoner is with the destination (or if they own a Key belonging to that realm), the more likely they are to successfully teleport to the exact location they desire. It may be possible to travel to a completely random or unknown (to the traveler) territory, but this can be dangerous and is not recommended unless the Lythian is part of an experienced adventurer/mapping party.
Groups of Lythians have come together across realms to create large organizations and guilds with various purposes. Large factions have developed with their own goals and frequently explore new realms to recruit members.
Outside of inter-realm organizations, individual realms may have developed their own organizations, governments, and societal practices. These vary from realm to realm (and may be even more intricate within the areas of the realms themselves) and the research of such information is something to which many dedicate their entire lives.
The barter system is king throughout many of the realms, and merchants are frequently willing to exchange their goods for information, stories, or other items that come from other places.
It is possible that some merchants or realms may not be interested in this currency, though they are typically special locales, or mysterious places that only appear during certain times of the year (event locations).