Fannabelta

Fannabelta was an elf that originally served Trimegistus and was his most loyal retainer and right-hand woman. She became his Intelligent Weapon and was sought out by Fran and Teacher to see if she could provide advice on how she retained sane for so long.

Synopsis
Contains spoilers for Web Novel chapter 1031, 1032 and 1039:

She lamented that Trimegistus would not abandon his duties to his people and was always sacrificing himself to help them as a ruler. She also was viewed with jealousy by political elites who wanted to separate her from Trimegistus so their own daughters could become close to him. Elves were also not accepted as equals but as mere servants. This frequently led to attempts on her life, but her relationship with Trimegistus was not as lovers but only pure loyalty.

She fell from an attack from multiple Dragonkin and became a test subject for Trimegistus' Intelligent Weapon project. She was the only one to retain her sanity because of her Devotion skill. Instead of countering Trimegistus' arrogant attempt at heresy she encouraged it (likely because of her transformation into an intelligent weapon and her feeling that little by little she was going insane). After Trimegistus was punished she resolved herself to remain by her master's side and her Devotion skill evolved into Eternal Loyalty. During a fight with Maleficent she had her Eternal Devotion skill stolen by him and because his exchange was too unequal Original Sin Envy was transferred to her. This drove her insane and resulted in Trimegistus deciding to destroy her.

In her final moments she felt thankful for Trimegistus setting her free, but worry for Trimegistus going forwards. Teacher from cannibalizing her gained the "Devotion" skill which he considered, along with the information about the "Eternal Loyalty" skill, a clue on how to maintain his sanity.