Chtholly Nota Seniorious

A leprechaun. Her race is also one of those called Markless.

Was the oldest fairy, and also the strongest wielding the sword of the Regal Braves, Seniolis.

As she uses her venom, her hair starts changing to red and she starts losing her memory.

Deceased in battle. For those wanting to pickup the Light Novels, it is Volume 3, Chapter 4 Part 5.

As can be seem by Ithea's history, the leprechauns are loop-reincarnating which means it will probably happen to Chtholly also.

It is implied that the scene of her as a baby at the end of the series is a flashback to the day she was born.