Arcturus Tower is a giant tower that looked as if it carved out of a giant tree inside out, complete with numerous branches full of leaves. The tower has at least one entrance, a balcony, and a rooftop. The only known interior of the tower is the room where Chariot and Croix monitoring Akko and her friends' progress as they chasing Noir Missile as it begin to progressively evolve into more serpentine form.
Around the tower is an open area which has a giant seal where Grand Triskellion contained. Upon unlocked, the seal would unveil a large, structure-like dome that opens into nine bud-like structure each possessing a nearly featureless masks. Suggestively, the structures represents members of Nine Olde Witches who formed the seal in the past.
Not much is known about the tower. Suggestively, the tower was created by Nine Olde Witches both to watch over Arcturus Forest and guarding Grand Triskellion.
Young Chariot and Croix gathered at the tower upon summoned by Woodward, who told them that one of them shall be tasked to unlock Seven Words of Arcturus with Claiomh Solais. To Croix's dismay, the staff instead chose Chariot instead of her.