HERAB SERAP is a fiend of a singular nature, for he was once known as Zapan, of the Dark Eight. He was the third of that name.
His journey up the ranks of the Ministry of Immortal Diplomacy was fairly standard, beginning as an erinyes (chosen as a promising spinagon) and being promoted to paeliryon status before finally becoming a pit fiend. When his predecessor became an unwilling tribute to Set (some say due to the machinations of Nybbas, then one of his cherished minions), the other seven members of the Eight voted for the one who would be Zapan to take his place.
The Taking of the Bridge of Gargoyles in the City on the Edge was a terrible event in the annals of baatezu history. At least, it would have been had Zimimar allowed the story to be written in them. As it was, it was still a great shame on the head of Zapan, who felt it was a personal failure of diplomacy on his part. The Bridge was part of a vital trade route between the city of Stenching Evil in Avernus, where nupperibos are sold, and Gehenna. When the tanar'ri gained control of it (with yugoloth help), the stockhouses bulged with unsold nupperibos. Some high-ups became afraid the extra stock might manage to evolve, and many reckless battles were waged in an attempt to kill them off. Even when the 'loths and tanar'ri inevitably came to blows, it was long before the City on the Edge and the Bridge of Gargoyles could properly be rebuilt and trade was fully restored.
Baalzephon, in particular, was furious, and during the next meeting of the Eight in Malsheem she insisted that Zapan step down or die.
Meekly, he did, allowing a new name to be branded on his soul. However, it seems the scars of his old name still remain, creating a palimpsest beneath the new psychic sigil. This means that occasionally spells directed at the current Zapan (both malevolent and benign) affect him instead.
Herab Serap found a position as an advisor to the mayor in the House of Ravens in the City on the Edge, which is built on the edge of Gehenna�s first furnace, where the Styx spills into the bitter void. From there, he learned the ways of the baatezu merchants and exiles who dwelt there, and used his growing wealth and influence to help them rebuild the burg after the inevitable tanar'ri/yugoloth war.
Through it all, he wondered why he was still alive. He was a danger to Baator, wasn't he? He knew any number of secrets, and was always learning more. Any number of assassins could have finished him off by now, if the Dark Eight or the Lords of the Nine wished it. So what was their intention?
Could it be that he had been set up? Perhaps the Bridge had been deliberately sacrificed to the tanar'ri in order to provide an excuse to send Herab Serap there. The exile couldn't put such a thing beyond his former colleagues. He had been, and still was, more than capable of such elaborate moves himself.
But for what purpose? Was he supposed to be some sort of spy? It could be that someone was recording everything he learned, perhaps through the flaw in his name. Perhaps he was a hostage, a gift to the yugoloths who control Gehenna as his predecessor had been a gift to Set.
Herab Serap became increasingly paranoid. Ultimately, he decided it was best if he showed his hand. He sent a long letter to Malpheaz, an ultraloth who styled itself the Master of Mungoth, spilling some of the secrets of his former colleagues in the Eight. Malpheaz seemed the perfect fiend for Herab Serap's purposes, far enough from both the City on the Edge and Baator to test exactly how much the rulers of the baatezu knew and cared about what he, Herab Serap, did.
Now he is more nervous than ever. Was this, too, what they wanted? The tall, gaunt humanoid often seen by the mayor's side in times past now spends almost all of his time in his personal chambers. Where once he bared a smile like pure treacle, now he keeps his expressions closely guarded. When he travels, it is in the form of a dust mephit. He is still a possible contact for those interested in Gehenna's baatezu underworld or in Baator's upper hierarchies, but he is certainly much harder to reach than before.