|“||The King falls, but I live forever!||„|
|~ Soul Master|
Soul Master is a major antagonist and boss in Hollow Knight. He was once the leader of the Soul Sanctum, who tried to use the power of the soul to immortalize himself to live through the Infection, but was ultimately driven mad from misusing the substance.
During the time of the Infection caused by The Radiance for the negligence in her worship, Soul Master and his students studied collecting soul from within the bugs' spirits, believing collecting enough would stop the Infection. The Pale King opposed Soul Master's idea and ordered him to cease his experiment, although Soul Master and his students continued to perform the experiment in secret from the king, with no knowledge of his usage of Void to seal away the Infection instead.
When the Hollow Knight managed to seal away the Infection, everything seemed to return to normal. However, it did not last long for the Infection to find its way out of its sealed state. Soul Master was inspired by prophetic dreams on a new way to use soul to avoid the Infection. Without the Pale King's advice, as he and his White Palace vanished following the Hollow Knight's sealed fate, Soul Master and his followers took more drastic measures to obtain soul by conducting experiments on various bugs of Hallownest to deprive them of their soul, believing enough will grant them immortality from the Infection's wrath, although most of the members were cursed from the misuse of soul and turned into creatures known as Mistakes and Follies.
Despite the thoughts of Soul Master and his students, soul was not strong enough to protect them from the plague and became infected. By the time the Knight makes it to the Soul Sanctum in the City of Tears, they were too late, as the Infection had made it through the sanctum and corrupted each and every member of the facility, including Soul Master himself, who faces the Knight at the end of the sanctum.
Due to all of the soul that Soul Master had obtained, he was a powerful foe for the Knight to handle, although the Knight managed to find a way to conduct and collect the soul, and used their power against the Soul Master, seemingly destroying him and exposing his soul. Before the Knight was able to collect it, Soul Master managed to recreate himself through his exposed soul and continued his brawl against the Knight but was defeated yet again, this time for good. The Knight once again collects Soul Master's soul and obtains the Desolate Dive spell, allowing them to slam through the floors of the Soul Sanctum and continue on their quest.
Optionally, the Knight can return to the Soul Sanctum and use the Dream Nail on Soul Master's corpse to enter the Dream Realm and fight Soul Master's Dream Boss counterpart, Soul Tyrant. He is one of the six bosses that can be refought in the Dream Realm, the others being False Knight, Broken Vessel, Dung Defender, Zote, and Grimm. Defeating Soul Tyrant grants the Knight 300 Essence to their Dream Nail.
- Soul Master is the only boss to give the Knight a spell after defeat, being Desolate Dive.
- Prior to update 22.214.171.124, Soul Master's slam attacks did not produce shockwaves.
- It is possible that the Radiance was the cause of the prophetic dreams that Soul Master was inspired from.
- In the game files, Soul Master is referred to as "Mage Lord".
- Since the Lifeblood update, Soul Master's size was slightly shrunk, though this may be a glitch.