During the "secret war" between sorcerers for the fate of humanity, Nefarian Serpine was one of the three generals under Mevolent's command. To kill Skulduggery Pleasant, Serpine kidnapped his wife and child, and murdered them both as Skulduggery watched. In rage, Skulduggery tried to retaliate with a dagger, which Serpine coated with a paralysing poison as he knew Skulduggery would attempt to use it. Taking advantage, he killed Skulduggery through his "agonising death" ability, which causes agonising pain to a victim before killing them. To strike a blow to the moral of the sanctuary's armies, he had Skulduggery's body hung on a pike and burned. Little that he knew that because the machination of the priest named Auron Tenebrae whom he prieviously blackmailed to give him Agonizing Death power has arranged that his newfound powers won't truly killed Skulduggery, but rather reduce his enemy's body into skeleton and his action creates Lord Vile in process as Skulduggery's split personality.
Scepter of the Ancients
As a strong believer in the dark godlike-entities known as the Faceless Ones, Serpine sought out to find the sceptre of the ancients, an ancient weapon which disintegrated the target into dust and was capable of killing a deity, to assassinate the elder council and use an artifact known as the book of names to locate anyone who would know how to summon the faceless ones to Earth. After learning the sceptre's location, Serpine killed Gordon Edgley for attempting to hide it from him, and sent an assassin to find a key which would grant him access to the cave system Gordon hidden it. However, his plans were delayed when the assassin was killed attempting to murder Stephanie Edgely, Gordon's niece.
To find out where the key was, Serpine abducted Skulduggery and tortured him until it was clear to him that even the skeleton detective didn't know where it was. Soon after, Skulduggery was rescued by Stephanie, now known as Valkyrie Cain, and a small group of allies. The rescue was a success, but Serpine managed to capture a cleaver, one of the sanctuary's elite soldiers. To test an experiment to make himself immortal Serpine killed the cleaver and returned him to live as an undead entity known as the white cleaver.
Knowing Skulduggery's main weakness was his loss of judgement when angered, Serpine dispatched the white cleaver to kill Valkyrie, who Skulduggery has formed an attachment to. The white cleaver failed to do so, but caused Ghastly Bespoke, an old friend of Skulduggery, to temporarily turn himself to stone. Soon afterwards, Sagacious Tome, a member of the elder council, revealed himself as an ally to Serpine and lured the other 2 members where Serpine could kill them, leaving the book of names vulnerable.
Knowing the whole world was at risk, Skulduggery and Valkyrie, along with their ally Tanith Low, went to the sanctuary to stop Serpine, but found he slaughtered everyone in the sanctuary headquarters and was already attempting to take the book of names. While Tanith fought the white cleaver, Skulduggery and Valkyrie confronted Serpine, after the latter killed Tome to completely remove the book's defences, and fought against him, eventually resulting in the book of names being destroyed in the fight. The white cleaver, now under the necromancers' control, witnessed Serpine's defeat and abandoned him. Skulduggery, having let go of his desire for vengeance, attempted to arrest Serpine for his crimes. However, Serpine refused to come quietly, and attempted to use the agonising death on Valkyrie, ignoring Skulduggery's warnings. As soon as Valkyrie's torture started, Skulduggery grabbed the sceptre of the ancients, and is forced to reduced Serpine to dust for good, avenging countless deaths, including his own, and saving his apprentice's life.