They wear a lot of black and grow their hair really long. Their favorite store is Hot Topic. They're preoccupied with death. That's because they're kind of in charge of it. Like Hel, many of the members of this clique are responsible for imprisoning, and sometimes even gathering, the souls of the deceased. You might call them the coroners of the cosmos. It's an unpleasant job, but somebody's gotta do it.
Kali's a bit of a chameleon: She has a lot of different personalities, or "aspects," to use the fancy Hindu term. One of her aspects is as a death goddess. Shortly after her birth on a battlefield, she became so frenzied in her killing that she began killing everything in sight. Kali's sword, constantly-bloodied breasts, and severed-head earrings aren't just the world's greatest and most gruesome Halloween costume; they're also reminders of her death goddess aspect. So is her preferred hang-out: cremation grounds, where dead bodies get burnt to ashes.
Some death gods are cheerful caretakers of souls. Whiro's not one of those. This lizard-god of Maori mythology inhabits a dark underworld. If you suddenly feel an irresistible urge to TP someone's car, blame Whiro. This guy can plant malicious thoughts in people's heads. He also feeds on the souls of the dead, growing stronger with every bite. One day, says Maori mythology, Whiro will grow so strong that he'll escape from the underworld and consume everything in sight. That's why the Maori cremate their dead. Why feed the beast?
Melinoe was, depending on who you ask, either a goddess or demon of the underworld. She sometimes walked the earth at night with a train of ghosts, terrifying people with her half-black, half-white appearance. Besides scaring people, Melinoe's job was to preside over offerings to the dead. Ancient Greeks invoked her name during these rites, asking her to bless them.