H'ronmeer is generally seen as the Martian god of death, fire and art, though he did once refer to himself as god of life and light. Despite being a god of death, he is not malevolent and cares about the Martian people.
Centuries ago on the planet Mars, the entire Green Martian civilization was wiped out by a plague commonly referred to as H'ronmeer's Curse. Although it was named after the Martian god, it was created by Ma'alefa'ak, the Martian Manhunter's brother. H'ronmeer had looked after the souls of all those Martians who had died in the plague for centuries while they were prevented from moving on by the Martian Manhunter's grief. It was H'ronmeer who revealed to J'onn the truth about the Martian people and revealed his prior beliefs about them to be lies he invented from pulp science fiction to cope.
In fact, H'ronmeer is actually a masculine aspect of Death, the member of the Endless, seven nigh-omnipotent personifications of the universe. This is similar to how another Martian god, L'Zoril, lord of Dreams, is an aspect of Dream of the Endless. It is possible that all Martian gods are in fact aspects of the Endless.
H'ronmeer is also worshiped and respected by the Red Saturnians as well. They refer to him as Hiromeer, most likely due to the evolution of their language from the Martian.