"Time Bomb"
Some kings and queens would also learn some space-related techniques to catch 'space and time trashes' to collect food for the huge amount of abyss demons in Abyss.
They could not leave Abyss, but they could lure things, either living beings or dead things, to enter Abyss.
Some even made some special channels that could accurately detect a newly transformed monster who was once a beast but was contaminated by the miasma released by the Abyss' entrances and exits.
Then, they would steal these monsters as food to barely keep the abyss demons alive.
The abyss demons died in a huge number every single day, but their reproduction rate was also too fast, just like an insect army or something.
This was what the previous kings and queens had to consider.
Anyway, they were focusing on making the Abyss a better place, but ever since the last king, which was Axelle's father, disappeared, no new king or queen came out among the abyss demons.