【Infernal】 , 【chthonian】 ,  【hellish】 ,  【Hadean】 ,  【Tartarean】 ,  【stygian】  mean of or characteristic of the abode of the dead.

【Infernal】  basically denotes of or characteristic of the underworld regions once held to be inhabited by the earth gods and spirits of the dead. Through confusion of pagan conceptions of the underworld with Jewish and Christian conceptions of hell as the abode of devils and a place of torment for the souls of the damned  【infernal】 has acquired connotations of horror, torturing fiends, and unendurable suffering through fire, which nearly always blur and sometimes blot out its original subterranean implications.

When the classical conception of the underworld must be suggested without an admixture of alien connotations,  【chthonian】 is sometimes used.

【Hellish】  comes close to the current meaning of  【infernal】  but carries so strong an implication of devilishness that it more nearly approaches fiendish in its meaning. 【Hadean】 , 【Tartarean】 , and 【stygian】 are used in poetry in place of  【infernal】 , sometimes without any reference to the conception of Hades, Tartarus, and the Styx in classic mythology.

Very frequently  【Hadean】  is a loose equivalent for  【chthonian】 ,  【Tartarean】  suggests darkness and remoteness,  【stygian】  connotes bounds with no outlet for escape, but all three are without fixed content.