Our IRL universe is one in that if you keep going in a certain direction, you can eventually reach your destination. Whether it be to the right, up, down, wherever your destination is, you can surely get there with the appropriate means of transportation. In the Drealms universe, however, it's different. This is the Realms system.
The entire universe of Drealms is split into circular realms. Each realm can vary in radius, some being only as large as a city, while others can span for miles upon miles. Nations and countries mostly span for about 4-10 large realms. They act like biospheres, with each realm having their own climate and day/night cycles. Neighboring realms sometimes share climates and time of day, however.It is nearly impossible to break out of the edge of a realm. If you go to the very end of one, you will be encountered by an invisible wall. To go to another realm, you must take a portal. Each realm has varying number of portals in them leading to other specific realms. For example, if you start in Realm A and you want to get to Realm C, you must first take the portal to Realm B then to Realm C. All realms connected to each other form a giant web of realms, and this web is the entire universe.
Realms can vary greatly with their contents. Some contain cities, others contain untouched nature. They don't have to be regular terrain, however. Some may contain oceans of lava, or just be a giant subterranean cavern. Some realms barely contain anything at all, and are just empty space.
It's possible to see other realms through another realm's wall. Looking beyond the wall of a realm gives you only the sight of pitch black darkness with floating chunks of terrain/skies. Realms with skies have clear view of realms cluttering up the sky, though this is largely or completely blocked by the color of the realm's sky and its sun(s) and moon(s). The color of the sky can vary between realms, going through the color spectrum. The darker the sky is, the easier it would be to see other realms. The number of suns and moons can also vary, with some even having moons cluttering the sky.
All of the Realms of the universe form a giant web. The central area of the universe are the more stable, safer realms. These realms are where most nations and people reside, as well as having the most regular terrain. They are also where most RP takes place. This area is simply known as Central Realms.As you go further away from the center of the universe, the realms would become more dangerous. These realms have powerful creatures and unsafe terrain. One realm in this area, for example, could be a cavern with toxic gas that would kill a human in minutes. Another could be a forest with giant, venemous snakes. These realms are known as Inner Realms.
Further away from the Inner is simply the Ocean Realms. These realms are simply oceans. Some ocean realms contain powerful leviathans, others contain peaceful coral reefs. These realms seperate the Central Realms and Inner Realms from the Outer Realms. Corthos has control over these realms, with his large naval nation Aecor.
The Outer Realms are the biggest section of the universe. They contain the most dangerous creatures, the most unstable terrain, and the Heaven Realms and the Hell Realms.
Finally, at the very edge of the universe is the God Realms. These realms are where the true forms of the Gods reside. Reaching these realms is nearly, if not completely impossible. Especially for a mortal who was born in the Central Realms, as they'd have to travese the Inner Realms, escape the clutches of Corthos in the Ocean Realms, and survive the Outer Realms.