The link you posted appears to be to a Greek or Russian Orthodox website. Your citation appears to refer to an incident from the Sayings of the Desert Fathers. Desert Stories from the Fourth Century
Abba Macarius the Great
Abba Macarius said, 'Walking in the desert one day, I found the skull of a dead man, lying on the ground. As I was moving it with my stick, the skull spoke to me. I said to it, “Who are you?” The skull replied, “I was high priest of the idols and of the pagans who dwelt in this place; but you are Macanus, the Spirit-bearer. Whenever you take pity on those who are in torments, and pray for them, they feel a little respite.” The old man said to him, “What is this alleviation, and what is this torment?” He said to him, “As far as the sky is removed from the earth, so great is the fire beneath us; we are ourselves standing in the midst of the fire, from the feet up to the head. It is not possible to see anyone face to face, but the face of one is fixed to the back of another. Yet when you pray for us, each of us can see the other’s face a little. Such is our respite.” The old man in tears said, “Alas the day when that man was born!” He said to the skull, “Are there any punishments which are more pain-ful than this?” The skull said to him, “There is a more grievous punishment down below us.” The old man said, “Who are the people down there?” The skull said to him: “We have received a little mercy since we did not know God, but those who know God and denied Him are down below us.” Then, picking up the skull, the old man buried it.'
It is my (Catholic) understanding that our prayers for the dead can aid the repose of only the souls in Purgatory; those in heaven and those in the hell of the damned are uneffected by our prayers. In current usage, hell refers to the abode of the damned but, formerly, it had a much broader meaning and referred to the abode of the dead in general, including Purgatory. Your citation appears to be from an older English translation and probably means the hell of the dead in the older, broader sense rather than the hell of the damned in the more recent, narrower sense.