Nosramus

Nosramus is a white haired alchemist living and studying in the dungeons of Fear & Hunger, but doesn't seem to radiate immediate danger and aggression. Something about his stature seems almost otherworldly or ancient.

Lore
Nosramus finds Le'garde interesting and knew that he himself planned his imprisonment. Everything that lead to him getting caught, taken down to this darkness and even the torture he experienced there. It was all part of his plan, so he can reach greater heights, unify the land, and lead mankind to a new era. Something that lasts beyond Le'garde himself.

The dungeons of Fear & Hunger is a special place, where someone could get as close to the gods as there. Like many before him, he wanted to use the power that dwells there. But unlike others, he already got all the keys to become something greater: Le'garde already achieved the state of dominance overground. He achieved the enlightenment with the cube he brought there with him. His dreams would soar endlessly with the new goddess visiting him in his dreams every night. And finally, the darkness and the torture he experienced there would rival that of the gods.

But Nosramus seems like he isn't telling the whole truth.

He was the fifth member of the Fellowship of the current New Gods. The now called "Forgotten One" has little written about and, depending on which version of the story is followed, was either deceived by the older gods or tried to trick the fellowship.

Behavior
Depending on your actions, Nosramus will be either friendly or hostile towards you (not in the sense of attacking you, but more so ignoring what you have to say). For him to be friendly towards you, introduce yourself when you first meet him in the cave west of the Mines, and don't hide in the shadows, or else that will offend him and potentially end any sort of interaction with him until you start up a new playthrough. It is especially recommended to not do this if you are trying to do Enki's Ending S run as interacting with Nosramus is needed to acquire the one needed object to achieve the ending.

Once you are within his room after defeating his bodyguard and faithful undead servant, simply go to him and talk. Don't even bother to try looking into his chest. He will warn you initially to back off from it but if you just go ahead and open and take whatever is in it, he will no longer talk to you and end any potential dialogue and lore information you might get from him and end the hardmode Enki Ending S run. After removing to his 2nd hideout nearby Salmonsnake's pool, you can check this chest freely, he will not be bothered.

Trivia

 * His name might have been taken or inspired by a man named Michel de Nostredame. His name is usually Latinized as Nostradamus. The man was a French astrologer, physician, and a reputed seer. He is known for his book Les Prophéties, which is a collection of 942 poetic quatrains that allegedly predicted future events and prophecies that will happen after his time.