With the summer update 2021 Yselda's character become more explained.
As per TibiaWiki she is" the betrothed of Kesar the Younger." 1 I believe this is due to Spectulus who describes her as "betrothed". However, in fact she is wife of Kesar the Younger. This makes her Queen of Bounac and a protagonist of the Adventures of Galthen- Galthen and the Lost Queen Quest. She is described as a honourable woman with a kind heart. 2
Her blood line seems to be cursed (genetic curse) which unfortunately was also inherited by her. The curse was involving a strange ritual which was described as follows:
Spectulus: ...remarkably memorable. A great curse seems to transform people into a form of... wooden facsimile of a human being. ...
Spectulus: Look, I know this sounds strange but a lot of the crude conclusions from the older mages rang true. ...
Spectulus: A form of biological curse forced females to tranform after giving birth, conduct a strange ritual on their children and... ...
Spectulus: Wander out into the dark, leaving everything behind. Never to return and ultimately to carry out a complete metamorphosis. ...
Spectulus: If that's what happened to Kesar's Yselda, she might have gone to find a place to fully metamorph. ...
This would meant that Yselda gave a birth to a child. Yet, it seems it was not the case as :
As per Tibia news teaser Galthen was asked to find missing noble woman. 3 The timeline is matching as it happened when Kesar Etzel was alive. As per Inkeeper Alphonse, Galthen actually helped firstly the "missing noble woman" get married to a knight, while she was pregnant (who is the father? knight or perhaps someone else?). The missing woman which Galthen was searching for is actually grandmother to Yselda.
Lesh the Seer: I showed Kesar what happened to his beloved. A curse, terrible and dark. She left to find answers to questions she didn't know the past planted in her. ...
Lesh the Seer: She lives, yet sits in the dark, still, without motion. Waiting, ever waiting and watching. I gave the king this vision, for he asked for it. ..
And upon defeating her metamorphing without healing her samplings she says:
Player: Hi
Yselda: You freed me, brave warrior... and you even saved my... children. ...
Yselda: I always wanted children in my life, I never... had... I never was able... to...ach! ...
1. https://tibia.fandom.com/wiki/Yselda
2. https://tibia.fandom.com/wiki/Adventures_of_Galthen_Quest
3. https://www.tibia.com/news/?subtopic=newsarchive&id=6141