This game was originally exclusively released in Japan in 1993, under the name Makaimura Gaiden: The Demon Darkness.
It has since been translated in the English language!
"A long, long time ago before humans starting appearing in the fictional place called the Ghoul Realm, there was a fictional, young ghoul warrior, a gargoyle named Firebrand from the town of Etruria. One day, while Firebrand was out partaking in his daily routine of training in a small, alternate dimension, The Black Light appeared unexpectedly and destroyed his home. When he returns from his training, he was told to hurry to the local King by another ghoul just before it collapsed and died before him.
Firebrand then made his way there. After defeating Nagus (the Spaulder-wearing monster as seen in the distance on the European box art), Firebrand was able to meet with King Morock, who informed Firebrand that he, himself, was on the brink of death. Before dying, he gave Firebrand the Spectre's Fingernail and Firebrand set off on a journey to unravel the mystery of The Black Light, facing off against an invading army the whole way."