Treyni

Treyni (トレイニー) is a Dryad that resides in the Jura Forest.

Appearance
Treyni has the appearance of a full-grown young woman with green hair and blue eyes along with well-defined facial features. She is an ethereal beauty whose body takes on a semi-transparent state. She wears a full-length aqua colored dress with white sleeves and goes barefoot.

Personality
As the overseer of the forest, Treyni possesses a certain dignity and level of grace befitting the role. She is well-spoken and intelligent, able to mediate between multiple parties with ease. Beneath that exterior, however, is a childish and emotional person, much like her master, Lamrys. Whenever she's around Lamrys, she tends to show her true self and spoils her excessively, greatly stressing out Beretta – the only sense of reason within the trio. Her personality is virtually identical to Rimuru Tempest, as commented by him, except she's way more skilled in avoiding commitments and passing on any troublesome responsibilities to others.

Due to her past as a refugee, Treyni is empathetic towards the suffering of others and is willing to provide her aid to those who come under her protection if they ask for it.

Background
Over a thousand years ago, before ever settling in the Jura Forest as a Dryad, Treyni was once a fairy serving under the Elemental Queen, Lamrys. She parted ways with the then Elemental Queen who reached the end of her lifespan, believing that the next queen succeeding her would be a wholly different person from the previous queen that only inherited her name. She came to the Jura Forest for refuge along with other fairies and were given permission to reside there by Veldora. To thank him, Treyni offered her services and became the overseer of the forest, meting out punishment to those that threatened its residents.

Trivia

 * In The Slime Diaries, Treyni is shown to have a fondness for potatoes. She also said that Dryads are born from potatoes leading to the obvious joke that Treyni might be a cannibal due to her near constant consumption of potato chips.
 * Treyni is shown to have awareness of Veldora being eaten by Rimuru, long before Rimuru himself shared the details with his friends and allies. In episode 12 of season 1 of the anime, she even said Rimuru has Veldora's Divine Protection.
 * Despite being a Dryad, she is shown to have a deep understanding between civilization and nature, and always gives her insight to best handle development of Rimuru City, and later, The Dungeon. Because of this, despite Rimuru City becoming highly advanced, the city layout is one with the natural surroundings and doesn't dominate the land.
 * She is one of the few monsters to already have a name at the time of her introduction.
 * Her laidback attitude and increasing tendency to involve herself with the affairs of Rimuru has been a point of envy towards her two younger sisters.
 * As Lamrys' assistant, she also has a strong fascination with technology and entertainment and helps to bring those and more to Tempest. She helps develop complex traps within The Dungeon. Upon hearing about video games from Veldora, she was shown to have an interest in trying to bring a form of it to her world. This could be seen as ironic, since Dryads are typically depicted in other media as tree spirits who're impartial to the flow of time. However, Treyni is always living in the moment mindset and strives to enrich her life every day.