Kupala is a young girl and member of the Forest Folk tribe that the party encounters during their explorations.
She is first seen during the third stratum exploration, where she warns the group to cease their advance at once, continuing to hinder their path with enemies as they continue to progress.
She is shown to bear some power, as she is able to summon the legendary guardians of the folk and can even blend into the forest to the point of invisibility. In Etrian Odyssey Untold, Kupala explains to the player that she is the priestess of the Forest Folk which would explain her importance and power.
She is the only member of the tribe that you can interact with verbally.
Kupala first confronts the party on the Azure Rainforest, demanding that the party turn back and soon vanishing in the cerulean woods. She's later found in the deepest part of the woods, where she summons , a powerful guardian, as an attempt to stop the party from descending.
On the , the forest folk lair, she explains how the humans and her tribe fought in the past, and made a pact of peace, which prevented humans to enter their lands. The party however, given a mission to slaughter them, ignores her warnings and moves deeper into their lands. They ultimately arrive in the lowest reaches of the desert, where the main army of the tribe is stationed. Kupala, in a last attempt to stop them, summons , another guardian of her folk. Upon their defeat, however, Kupala is disheartened, to the point of giving up on fighting the party. She vanishes in the woods, never to be seen again.
In Untold's Story Mode, however, her role in the story increases greatly. In it, it’s revealed that the members of the Forest Folk are being driven mad by the corrupt core's miasma, which is at first believed to be a malady. Even though the party seeks to cure them, by slaying the core, Kupala is extremely wary of them, and unwilling to let them get past their grounds, since their descend would unavoidably end up killing countless of her kinsmen. She also reveals that the god of her tribe lives in the depths of the labyrinth, and for such she will must protect it and stop them.
By the time the party defeats Iwaoropenelep, she's exhausted, due to the massive amount of energy she uses to summon the bird and faints. The party carries her back to Etria, where she recovers herself, and becomes a Guildkeeper to repay her debt with them, while waiting her powers to return.
When the and the others finally reach the mighty core, their original plan of using a poison made by Visil to kill the creature fail, as the beast recovers its full power soon after. Kupala arrives at the scene, revealing her tribe's true purpose: to help in defeating their god, revealed to be the core. She sacrifices herself to join her spirit with the Highlander's spear, highly empowering him and his allies. With her help, they finally succeed in destroying the creature.
Despite her death, Kupala is still available on the guild house during the post game.
After you defeat in Story Mode, she'll join as a guildkeeper. Her (EOU) enhancements will summon a guardian beast of the Forest Folk to aid you in the battle, using a skill of theirs in the end of the first turn of every battle. This can be helpful in random encounters when trying to keep battles short.
At first, Kupala is depicted as being harsh, always speaking with a high, imposing tone, and often threatens your party.
However, as you beat her and move her into the guildhouse, she changes into a more soft nature, and even explains her reasons to the explorers, showing her willingness to reach a peaceful solution.
In Untold, she is shown to not be as cold as she first seemed, as she was only worried about her people and her god. She is shown to have some affection toward the party, and even sacrifices herself to help them in defeating her god in the end.
As a guildkeeper, she will initially be quite cold, but her mood and kindness begin to show more as her power returns, culminating in her promising to use the power of Iwaoropenelep to protect the party.