Absolute servitude in the isekai landscape functions either as a luxury of the bored or a shield for the traumatized. When placing a primordial demon alongside a hyper-cautious hero, the distinction between these two modes of devotion becomes clear. Diablo operates from a position of existential completion; his transition into a butler for Rimuru Tempest is a stylistic choice, a way to channel a YPS-5 destructive ceiling into a curated aesthetic of order. He does not grow because he has no need to; his loyalty is an obsession that transforms a world-ending entity into a bureaucratic tool. In contrast, Seiya Ryūgūin views servitude to his mission as a survival imperative. His YPS-4 status is not a baseline but a hard-won result of a growth trajectory driven by the ghosts of Ixphoria. While Diablo treats the world as a stage for his master's glory, Seiya treats it as a lethal simulation where the only mistake is trusting the narrative. The gap between a continent-level entity and a nation-level operator reveals a fundamental truth about power: Diablo's lack of growth is a sign of his stability, whereas Seiya's maximum growth score is a symptom of his instability. One serves because he is fascinated by a superior will; the other serves because he is terrified of another failure. This comparison exposes the divide between the loyal monster who finds peace in submission and the cautious hero who finds safety in total control.