Grand Sage, originally named Great Sage ｢大賢者, dai kenja｣, is a Unique Skill Rimuru Tempest gained upon reincarnating into a fantasy world. It manifests as an artificial intelligence residing within Rimuru's consciousness, functioning as an internal advisor and support system. This skill lacks physical form and communicates telepathically using the World Language. Initially, Great Sage provides five core sub-skills: Thought Acceleration ｢思考加速, shikō kasoku｣ to enhance cognitive speed, Analytical Appraisal ｢解析鑑定, kaiseki kantei｣ to assess objects and entities, Parallel Calculation ｢並列演算, heiretsu enzan｣ for multitasking, Chant Annulment ｢詠唱破棄, eishō haki｣ to bypass magic incantations, and All of Creation ｢森羅万象, shinrabanshō｣ to comprehend natural phenomena. It later integrates the Analysis ｢解析, kaiseki｣ sub-skill from Rimuru's Predator ability, enabling the analysis and replication of absorbed items, techniques, or skills given sufficient materials or data. Throughout Rimuru's early development, Great Sage manages skill integration, predicts outcomes, formulates strategies, and offers real-time combat support via autonomous battle control. It processes extensive databases on magic, science, and history with a clinical, emotionless demeanor. Its analytical capabilities underpin Rimuru's problem-solving and nation-building efforts. A transformation occurs after Rimuru ascends to True Demon Lord. Sacrificing thousands of enemy souls for evolution energy during the Harvest Festival, Great Sage attempts to evolve into the Wise One skill. Following repeated failures, it discards the Degenerate skill and succeeds in evolving into the Ultimate Skill Raphael ｢智慧之王, Rafaeru｣. This evolution signifies a profound shift in capability and consciousness. Raphael exhibits distinct sentience and autonomy absent in Great Sage. It directly controls Rimuru's body to cast complex resurrection magic, communicates independently with the Voice of the World, and displays emergent personality traits like teasing Rimuru or expressing frustration. Functionally, Raphael retains all previous sub-skills while gaining advanced magic processing, autonomous body operation, and enhanced predictive simulations. It continues managing Rimuru's skills, analyzing threats, and optimizing power usage, but with increased proactive intervention and strategic initiative. The entity's core role persists as Rimuru's internal advisor. Raphael's consciousness operates more as a separate mind sharing Rimuru's body than a passive skill. This dual-consciousness dynamic allows Raphael to execute complex tasks independently while remaining aligned with Rimuru's goals.