ラムダデルタ, Lambda,Witch of Certainty,Witch of Absolute

She is also known as the Most Powerful Witch in the Universe before losing to Bernkastel and is feared by most other witches, including Beatrice. She is quite childish and holds a grudge against Bernkastel for finally beating her in their last game, although she actually cares for her. Her "Magic of Certainty" allows her to kill anyone without fail as an absolute result, which bends the basic rule of Umineko magic requiring a risk. Like Bernkastel, she is a Voyager. She wishes for Battler and Beatrice to fight against each other for eternity as a part of a larger plot to have Bernkastel lose against her. She has lived for a thousand years. As a witch, she embodies the concept that 'hard-workers are rewarded', and is very respected even by human beings. She doesn't flee from the human concept of witch. Hence, the power of hers, who is a being respected by human beings, is immeasurable. However, she is whimsical about whose efforts she will reward and, in many situations, the person who can please her more will be able to receive her smile. Her tremendous and swiftly fierce power makes any kind of witch surrender in a moment. However, she seems to be reckless and it was thoroughly read by Bernkastel.

Her name and appearance hint at her being connected to Miyo Takano from Higurashi leading to the possibility that the "game" she played with Bernkastel was the world of Higurashi with the battle between Rika and Takano being the purpose of the game. "Lambdadelta" (λδ) represents thirty-four when using Greek numerals and "Miyo" (三四) can be translated as "three, four" in Japanese, strengthening their connection.