Merasmus

 "Demoman! Would you have your eye back? Come find me!"

- Merasmus

"Merasmus" (Merasmus the magician) is the Red Soldier's former roommate and keeper of the Bombinomicon. In the Bombinomicon comic, when the RED Demoman was seven years old, he discovered Merasmus while seeking work. Ultimately, the Demoman lost his left eye to the book, and Merasmus was forced to remove it. Years later, the magician's tumultuous relationship with the RED Soldier was revealed, and he summoned MONOCULUS for the RED team to fight. During the events of Soldier Needs a Home, Merasmus kicked the Soldier out of his castle for being a nuisance. When he found later that the Soldier trashed his home and evicted him, he took on a ghostly form and decided to attack the Soldier's team. Merasmus (stylized as MERASMUS!) makes an appearance in the game as the boss the players must fight in Ghost Fort.

Trivia

 * Despite of he "Magician" he more actually closer to a Chaotic Villainous Warlock or Neutral-Bad Wizard because ethier appearance or personality those of wizard or warlock; Put seek vengeance on Red soldier only since trash his castle-home with lot of racoons; That get Merasmus nearly into demi-lich that only goal is to kill his former roommate and demoman faking the "Premise to give his eye back" that actually kill demoman too.
 * And according to TF2 Wiki he Re-used snipers animations and bit of heavy animations too (dance only).
 * As mentioned on the official wikia, the name Merasmus is a reference to the starvation disease Marasmus.