Heinrich Hein (ハインリヒ ハイン Hainrihi Hain), also known as the Angel Killer, was a legendary, unbaptized hero who defeated the vile, corrupt Monster Lord Alipheese Fateburn VIII (Eighth), also known as Black Alice, 500 years prior. He was able to master the Four Spirits and their elements, and is the creator of the Quadruple Giga and Element Spica techniques. He is also the ancestor of Marcellus and Luka and the original wielder of Angel Halo.
Heinrich's beliefs seem to indicate that he was, like his descendants, a pacifist and thought coexistence between monsters and humans was possible. Tamamo reveals that like Luka, he discovered that Goddess Ilias was the instigator that denied coexistence and fought against her and the armies of Heaven. However, he did not come to the Four Spirits for aid in this campaign (not wanting them caught in the crossfire), and despite his skill, met his demise.
Monster Girl Quest trilogy
Receiving the Angel Halo from Seraph Lucifina, who would later become a fallen angel, Heinrich set out on an adventure to stop the tyrannical Black Alice. Using the power of the Four Spirits, Heinrich defeated Black Alice as a means of bringing peace to the world, and was then, according to popular belief, ascended to Heaven by Ilias. However, this was revealed to be a false rumor; what really happened was that sometime after his battle with Black Alice, Heinrich left the Four Spirits and revolted against Ilias, trying to fight against her and her angel army alone, creating an incident known as the "Angel Massacre." He was able to defeat most of them, earning the nickname "Angel Killer," but eventually their holy energy and that of Angel Halo completely eroded his body and his soul was sealed into the sword. Ilias extracted and sealed his spirit in the Sealed Sinner’s Prison for all eternity; the ultimate punishment where one cannot reincarnate. It is also revealed that Ilias saved Black Alice in need for her plans, though this is mostly vague.
Lilith & Lilim, whom were sealed 500 years prior, inexplicably refer to Luka as Heinrich’s descendant, claiming that he sealed them with the Angel Halo and that Luka’s looks, smell, and power resemble Heinrich’s; Luka does not learn of the hero’s name, as they despise him so much they refuse to remember it. They also inexplicably mention that Heinrich destroyed all of Black Alice’s love, though this is never explored.
As Luka nears the Sealed Sinner's Prison the first time, the Angel Halo suddenly shines with a bright light, seemingly reacting towards Heinrich’s spirit. Sylph also mentions that the area smells like her former master.
Granberia later claims that Luka’s power matches Heinrich’s, further foreshadowing the lineage.
A discussion with Micaela confirms that Luka is a descendant of Heinrich, clarifying that Luka’s father Marcellus was the carrier of his bloodline.
After Ilias declares war on humanity, Luka and Alice try to record data of how Ilias sealed Heinrich in an attempt to borrow its holy energy. During the process, Heinrich’s soul appears, due to the interference caused by Alice. While they are surrounded by Chamaeru, Granaeru, Runaeru, and several Veteran Angel Soldiers, the ghost single-handedly eliminates all the angels using his own soul and Luka's body, much to their shock as one by one they fall to the Angel Killer. Heinrich explains that, while Luka's physical prowess and agility exceed Heinrich's, Heinrich still surpasses Luka's skill in handling the Four Spirits, and displays the use of Quad Spirit Summon, Element Spica, and Quadruple Giga; Luka comments that Heinrich's Quadruple Giga is at least twice as strong as his. However, Heinrich's soul has worn out and begins to fade, but Heinrich deems his descendant as the successor of the Hero's Soul and tells him not to be a failure like him, that a hero must save the world and return to those who are waiting for him, before vanishing.
- According to Undine, Heinrich took at least one year to master the power of water.
- The true outcome of Heinrich's and Black Alice's battle (whether Ilias directly intervened or not) and how Heinrich discovered Ilias being the true enemy is never explained through the course of the game.