Great Sage (大賢者 dai kenja) or Wise One (
Great Sage is a Conceptual Intelligence that has a heartless and emotionless personality and is solely driven by purely logical computations. It cares for nobody but the benefit of its master, Rimuru, even going so far as to hide things from Rimuru if it deems it beneficial to him in the long run.
Initially, Great Sage could only respond in a fashion where it asked Satoru Mikami [YES/NO] questions about activating his skills. It could not converse further than that.
According to Great Sage, after Satoru's soul had settled in the Slime body, it needed 90 days to "establish" itself. Till then, it was accessing and usurping the voice aspect of the Voice of the World. Thus, for quickly utilizing Satoru's skills, a response function was added, and it could answer any of his questions in properly structured sentences. Normally, a convenient skill that answers any questions doesn't exist. So, to answer his questions, it was trying to find a way to attain that particular function, so as a result, the Conceptual Intelligence mutated.
Although it was finally able to answer questions, it normally remained passive and lacked ego: it wouldn't answer unless asked in most situations, though it can act proactively when it concerns improving Rimuru in some way, even if it's in the long term, like how it developed the training of Veldora and Ifrit who were guaranteed to be Rimuru's allies later, or conducting experiments like testing if names can be overwritten - and most importantly creating an unprecedented procedure that prevents any permanent losses to happen during naming ceremonies.
After knowing about "Chant Annulment" and "All of Creation," Satoru linked the ability of Predator's "Analysis" and Great Sage's "Parallel Processing" to improve analytical capability. As an experiment, he first tried out the new ability to scan the Hipokte Grass he had been 'eating for 90 days. Establishing the link made analysis takes 1 second and the production of restorative items 3 seconds. Without the link, it takes 50 minutes.
- Thought Acceleration (思考加速 shikō kasoku): Raises thought-processing speed by a thousand times.
- Analytical Appraisal (解析鑑定 kaiseki kantei): The ability to analyze and appraise a target.
- Parallel Processing (並列演算 heiretsu enzan): The ability to detach thoughts and analysis of phenomena. Detached thoughts are also under the effects of Thought Acceleration.
- Chant Annulment (詠唱破棄 eishō haki): When using magic, the chant is no longer necessary.
- All of Creation (森羅万象 shinrabanshō): The ability to comprehend any non-concealed phenomenon in this world. Depending on the things the user understands and the information the user knows about, additional information can be inferred. In other words, the user needs to see it (the phenomenon) at least once.
- Analysis (解析 kaiseki): The absorbed target is studied and analyzed. Craftable items can then be produced. If the required materials are present, duplicates can be produced. In the case of successful skill or magic analysis, the same technique can be acquired. Originally a part of Unique Skill Predator was transferred over to Great Sage when Predator evolved into Unique Skill Gluttony.
- Auto Battle Mode (
自動戦闘状態ōtobatorumōdo): By giving permission to Great Sage, Rimuru can let it control his body temporarily.
- In the Anime adaptation, Great Sage utilizes the Voice of the World to speak, which is voiced by Megumi Toyoguchi in Japanese and Mallorie Rodak in English.