Hell fires are often used to describe the fiery depths of the underworld, where the punishment for sins is eternal suffering. However, there are many synonyms that can be used to describe this concept. One common phrase is "eternal flames", which emphasizes the unending nature of the punishment. Other phrases like "inferno" and "fiery abyss" emphasize the intense heat and flames associated with hell. "Brimstone" is another word often used to describe the sulfuric fumes and smoke that emanate from the underworld. Ultimately, each phrase has its own unique connotations, but they all evoke a sense of terror and judgement associated with the afterlife.