Gregorovic was a fatally ill human of the Fourth Age, who was desperate to avoid death. In the hope of prolonging his life, he captured some Cwyir elves and employed torturous experiments in order to find out the secret of their long lifespan. His work was unsuccessful, and he believed that some sort of "elven magic" beyond his comprehension was responsible (Seren had blessed the elves with longer lifespans).
When this failed, he sought out the Mahjarrat Sliske at the Barrows, and offered him his soul in return for eternal life. Sliske accepted his offer, but questioned whether Gregorovic had thought his proposal through. Sliske then killed Gregorovic and resurrected him in a monstrous new form resembling a macabre jester. Gregorovic was initially horrified and told Sliske that he had made him a monster, but Sliske slyly told him that he had always been one. Sliske then instructed him on how to maintain this form, and upon learning that he could become even stronger, swore fealty to the Mahjarrat.
When The Heart was discovered, Gregorovic was one of the five generals to arrive. Helwyr and the Twin Furies both swore revenge on him for the deaths he had caused. He then summons Sliske's wights to claim the Heart in his name.
When fought in Sliske's Endgame, Gregorovic uses a different set of attacks, and unlike the encounter in the Heart of Gielinor, his attacks do not poison.
Healing spirit: Gregorovic may occasionally call for a healing spirit which will dart towards him; if it touches him, it will heal him for 10,000 life points. If Gregorovic was not defeated first, the spirit will heal 20,000 life points instead.
Knife throw: If Gregorovic was not defeated first, he can perform his knife throw attack (where he tosses his glaives in the air), acting the same as the one he performs in the Heart of Gielinor.
Clones: If Gregorovic is the last enemy standing, he can summon shadows which are the same as those encountered in the Heart of Gielinor.
At 0% reputation each kill is worth 87,972.74 coins in uniques alone, if the player has 100% reputation this number increases to 175,945.48 coins.
^ abcdefgThe drop rate of this item can be increased with faction reputation. At 100% drop increase, the drop rate of this item is doubled. The drop rate of this item is increased in challenge mode. The drop rate of this item has its denominator multiplied by 0.99 when wearing a Luck of the Dwarves ring.
Gregorovic's design was inspired by Voldo from the video game series Soul.
As a human he resembles Walter White from the TV series Breaking Bad, including being terminally ill and being willing to use science for unethical purposes.
In a Developer Q&A about Heart of Gielinor, Gregorovic was quoted as being "not needed" by Sliske until now.
In the concept art Gregorovic is referred to as "the Mannequin".
After killing Gregorovic, the Adventurer's Log will say: "I killed the blade wielding terror, Gregorovic." Killing more than one Gregorovic results in the Adventurer's Log saying: "I killed # Gregorovics, all blade wielding terrors."
Gregorovic's combat level randomly changes anywhere from 1-1000 during the course of the fight; this does not seem to affect his actual strength in any way.
In the lobby area in an instance, if no one enters the arena, Gregorovic will repeatedly say "I'm so lonely." until someone enters.
Gregorovic's weapon, the Shadow Glaive, is based on the weapon from the British film Krull.
During the fight with Gregorovic, Akrisae the Doomed with one million life points may rarely appear and start attacking the player. The conditions required for this to happen are unknown.
As of 1 February2018, the highest kill count for this boss was 51,937 kills for normal mode and 1,490 for hard mode.
This had increased to 51,948 for normal mode and 1,851 for hard mode by 6 May 2018..
^Mod Shauny. Top 10 killers per Boss. 2 Feb 2018. "Here are the top 10 kills for each Boss in RuneScape, be aware that we've not listed display names for privacy purposes however if you wish to brag about one number being yours then we won't stop you!"*
^Mod Shauny. Top 10 killers per Boss. 6 May 2018. "Here are the top 10 kills for each Boss in RuneScape, be aware that we've not listed display names for privacy purposes however if you wish to brag about one number being yours then we won't stop you!"