When Gauldoth prepared to wage war against Malvich to obtain the Deadwood Staff, he wanted to send a messenger and ask the vampire to give up the staff freely, preventing any bloodshed. But first, he needed to find someone who knew nothing about his army, and therefore couldn't be interrogated by Malvich. He rode into a nearby village to see if they had any corpses he could use, but the policy in Nekross was that the dead were shipped directly to Nekorrum or other storage crypts, so they had nothing to offer him.
Gauldoth told them had he regretfully had to demand that they bring him someone - preferably a volunteer - to serve as his messenger. He held up two bags of gold, one for the village and one for the family of the victim. A few minutes later, Hadrin stepped forward. He was barely forty, but his lungs had been damaged by a disease, so he was weakened and unable to care for his family. Gauldoth slit his throat and threw him over his horse, then took him away to raise him as a zombie. He then gave the undead Hadrin a letter and told him to deliver it to Malvich.
Hadrin returned a few days later. Malvich had cut off his left arm to send a threatening message to Gauldoth - the left side of Gauldoth's body was living. Malvich had told the zombie that the staff had been in his possession for almost 700 years, and would remain that way for another 700. "The only way that you, Gauldoth Half-Dead, or your master are going to see it is when I use it on you!" Hadrin informed Gauldoth that, while waiting to meet Malvich, he'd talked to the other undead and learned that the Deadwood Staff had the power to kill both the living and the undead. Grateful that the zombie had warned him about the danger, Gauldoth appointed him as his new bodyguard.
Gauldoth soon killed Malvich and delivered the staff to his master Kalibarr, then followed him in secret as Kalibarr went to the Plane of Death. Here, hed learned that Kalibarr secretly served a God of Death that wanted to slay all living things. In a few months, Kalibarr would use the Deadwood Staff to release a magic force known as the Unholy Breath. Gauldoth returned to Axeoth and pledged to kill his master to save the world.
As Gauldoth prepared for the fight, Hadrin set up a garrison, known as Hadrin's Stand. Here, Hadrin and a group of loyal kreegans would prevent Kalibarr's forces from passing through. Sadly, one of the demons was bribed to open the door, and the garrison was overrun. Gauldoth first heard that Hadrin had been slain, but later learned that he'd been taken to the Plane of Death to be tortured for all eternity. Hadrin and the other zombies were staked to the walls of a cave while gargoyles taunted them and tore at their flesh. Enraged by the news, Gauldoth brought his forces to the Plane of Death and freed the zombies.
Gauldoth and Hadrin were able to defeat Kalibarr, preventing the God of Death from slaying everyone on Axeoth.
Hadrin appears only in Heroes of Might and Magic IV.