We do not know much about Koshei so far- despite of him being very known ( he is described in the book Famous Inhabitants of Darashia Book ) and forthcoming person, he was rather mysterious person. It seems he was very found with necromancy and his amulet which he was wearing, was his own protection from the undead. In Koshei the Deathless Quest Kosheil has a form of a Lich which suggest that Koshei has mastered Necromancery ( as per Tibia Library: "To become a Lich is the ultimate goal of all those who follow the dark path of necromancy, and there is no one among these lost souls who would not give his life gladly in exchange for the immortality and the frightful powers of these undead wizards") (Source: Tibia)
"<You have found this very old book that seems out of place among the other books.
As you leaf through the yellowed pages you see the description of a person on each left side and the painted portrait of this person on the right side. One person catches your attention. Not only does he have an inappropriate title, also his appearance is strange - on the one hand, he looks friendly, almost funny - on the other hand, his eyes seem to look directly into your soul. Eye-catching is the amulet he is wearing. You read the following and feel very uncomfortable with the portrait staring at you. You tear out those two pages and take them with you after having made sure nobody is watching you.> - First Page
"Lord Koshei the Curious
-_-_-_-_-_-_-_-_-_-_-_-
Date of birth: unknown
Age: unknown
Hometown: unknown
Date of death: unknown
There are not many things known about this man. He appeared out of nowhere and lived here for nearly ten years. Even though he was communicative, he never told anything about his profession or what he did for a living. First he lived in Darashia 2, Flat 11 for about two years. During that time he was roaming around, travelling the lands of Darama and often visiting the Bath of Dreams and the minotaur pyramid in the North.
Then it was discovered that he had built a tower south of the mountains. It is unexplained how he managed to do that because no one has been seen to help him. Anyway, the remains of his tower are still there. ..." - Page Two
...He often paid Drefia a visit which was a blooming haven during this time. Rumour has it that he has something to do with it turning into an undead city. These rumours are mainly based on his interest in the pyramid to the north, which is known to have been created by the bonelord race. Needless to say that these creatures are also linked with the appearance of undead creatures.
His interceders say that he was always a man of belief that never had anything evil in mind. He was often seen in the crypta of Darashia to pray to the gods.
As quickly as he had come, as quickly he disappeared and was never seen again." Page 3
References:
https://tibia.fandom.com/wiki/Famous_Inhabitants_of_Darashia_I_(Book)
https://tibia.fandom.com/wiki/Famous_Inhabitants_of_Darashia_II_(Book)
https://tibia.fandom.com/wiki/Famous_Inhabitants_of_Darashia_II_(Book)