FIG | THE LAND OF UNKNOWN WORLD

The solar system was once home to a remarkable total of 17 planets, all gracefully orbiting a colossal sun. In the distant past

 For now only 15 planets remain, Two planets were merged forcefully; Arkatra was one of them and the other was named Devsuna, the planet where all the monsters resided. The power level of Devsuna was so immense that it completely destroyed Arkatra's population, solely because Devsuna was the last planet in the solar system.

The inhabitants of devsuna didn't get proper food, and for water, there were only frozen lakes, or even the sea was frozen. They had to eat ice cubes to feed their bellies while enduring excruciating hardship daily. However, fate took a drastic turn when Devsuna fused with Arkatra. That day, the monsters on Devsuna didn’t hesitate to eat the other living beings of Arkatra, and before the barrier was established, it was too late; 75% of Arkatra's population was wiped out in mere three days.

The monsters simply couldn’t control their feelin and were driven to madness by their desperate hunger. Some didn’t survive the Harsh sunlight that they had seen for the first time in millions of years.

That was the time they called the golden age of Devsuna; for Arkatra, it was their worst nightmare. 

The losses were so extensive that the remnants of Arkatra’s civilization were thrown back by centuries.

In this solar system, every planet boasted unique species, advanced technologies, magical innovations, and distinct ecosystems.

 One planet, however, met its fate by being wholly consumed and obliterated by the sun.

Many things were common between planets, but the most common and dangerous was that every planet had at least one teleportation portal which they can go to others planets.These portals served as vital conduits for sharing knowledge, yet some planets misused their power, engaging in interplanetary conflicts.

Note: planets had to await their neighbors alignment for teleportation.

Arkatra was also one of the planets that shared their knowledge about magic and many essential infrastructures for stable living; however, in the end, Arkatra lost their portal location. During the merge they were unlucky and lost it.

But the monsters of Devsuna didn't know how to use their portals and was completely cut off from the teleportation lines from the start, which was also the reason many other species from other planets survived until now.

Note: The average lifespan of an Arkatra human was 200 years.

 while Devsuna's monsters lived an astounding 2 million years of lifespan.

As for the other species, they had their own different lifespans.