Gallows, the Death Ruler, emerges as a major antagonist across the anime's first two seasons. He exists as the true buddy monster bound to Magoroku Shido through a card serving as an interdimensional portal. His serpentine skeletal form dominates with massive silver talons on its left hand, a tattered red scarf draped around its neck, and thick black horns flanking its skull. The creature's lower jaw splits into twin tooth-lined mandibles reminiscent of insect anatomy. Gallows wields "Shadow Dive," an ability manifesting as thorn-covered vines erupting from his back to ensnare opponents directly, bypassing their guardian monsters. When inflicting damage, his "Soul Absorption Chain" activates, siphoning life force. An alternate evolution, "Gate Guider, Gallows Gestus," amplifies his physique with heightened musculature, jagged shoulder and back spikes, and bladed arms. His personality drips with mockery and contempt, particularly toward humans. To taunt Shido’s authority, he initially reveals himself to Genma, Kemura, and Sylph in a deliberately diminutive guise rather than his true terrifying form. He exhibits zero loyalty, openly ridiculing Shido’s failures. When Shido faced fatal descent from the Buddy Police building, Gallows coldly promised his buddy skill only "if he makes it"—a pledge he broke despite Shido’s survival. Key involvements begin in Season 1. Episode 40 marks his first visible manifestation, where he undermines Shido by appearing small before unveiling his skeletal horror. Later, in Episode 43, he scoffs at Shido’s terror during Disaster’s base assault. His ultimate betrayal crystallizes as Shido plummets from the Buddy Police building; Gallows admits withholding his buddy skill and mocks Shido’s desperation. By Season 2, Gallows transitions into Shido’s combat enabler. To conceal Shido’s identity while accessing Hundred Demons power, Gallows fuses with him—and occasionally Sofia—transforming them into "Death Shido." This fusion covertly channels the Hundred Demons' strength during battles.