Nyrissa is the main villainess of the RPG videogame Pathfinder: Kingmaker, based on the Pathfinder tabletop rpg. She is a powerful nymph with the Sorcerer7Mystic Theurge classes who turned to villainy after the Eldest of the First World dimention tried to assassinate her and exiled her love into a plane of shadows. She also appears in the original Kingmaker adventure module for the tabletop game.
Nyrissa is a powerful nymph of the fey realm of the First World. She fell in love with one of the Eldest, the rulers of the realm. She grew in power, earning the title of Nymph Queen, and eventually proclaimed herself to be a new member of the Eldest.
The existing Eldest opposed her claim and sent a Jabberwock to kill her. She managed to survive that attack (and later used the blood to create a Lesser Jabberwock), but was forced to submit to other punishments. Their judgment was swift—they tore from her mind and spirit her capacity to love, coalesced these powerful and deadly emotions into physical reality in the shape of a magical sword called Briar, and then cast the sword into the Material Plane where the nature of reality would hide Briar forever beyond Nyrissa’s sight. Their punishment extended to their fellow Eldest as well, whom they suspected had used Nyrissa all along as an experiment. Her Eldest lover, Count Ranalc, was exiled to the Plane of Shadow.
Nyrissa has a long-standing project to transfer a portion of the Material Plane that is coterminous with her fey realm of Thousand Breaths into the First World. She hopes that such a coup would appease the Eldest and redeem her in their eyes. This has dire implications for the material lands concerned, which form part of the River Kingdoms and the Stolen Lands.
At the beginning of the game, she poses as a kind hearted spirit of the forest who manipulates the player character into killing the Stag Lord, who was trying to stop her plans before she drove him mad with her whispers. Then she sets up a trap for the PC by luring him/her away from the party with the promise of a reward, revealing her true colors to him/her and then summoning a Hydra, a Manticore and a few Redcaps. The PC manages to sneak past the monsters and escape thanks to a potion of invisibility.
The PC and his/her party then began a journey to investigate Nyrissa's activities and stop her from merging the material plane with the First World.