Hell, also referred to as Inferno (LINE Webtoons, possibly a sloppy translation) or the Underworld, is the place where human sinners and heretics go after death, and where gods go to resurrect if they are killed. Hell is gigantic; some areas are full of sinners, and others are practically empty. The flow of time in the lower levels progresses at a much faster rate than in the human realm.
Agni is the king of Hell, but he never appears to take this role too seriously. When not in the human realm, he is often shown either sleeping in Hell or lounging around in the god realm. It is here in Hell that Agni's weapon is kept. In an earlier version of the finite, Agni is seen sleeping under a sign that says "Access Prohibited - Sword of Hellfire". Meanwhile, his work is done by Yama and Brahma.
For humans, there is both a normal afterlife and Hell, which are different. In Hell, time flows more quickly than in the human realm. What would be only a moment for living humans can be a very long time for those who are suffering in Hell. This is why the gods who hang around in Hell, such as Agni, have existed longer than other gods.
In the finite, it was stated that suras, after death, cease to exist along with the power of their name, thus preventing them from reincarnating. However, in the webtoon, Sagara claims that nastikas go to a special afterlife after death, where they are isolated from other beings, and that the 5th-zen gods have kept this information hidden. Agni, however, warns that it is not an afterlife but a separate dimension where a nastika's soul is ripped away from its name; any nastika that is reincarnated will have power, but no mind.
Apparently the primeval god Brahma likes the spot near where Agni's weapon is stored for her personal sauna. An earlier version of the finite describes how other gods also enjoy the sauna-like conditions in the same region of Hell, and would make efficient use of their time there by bringing along their paperwork.