It had evolved from Unique Skill Sage during his death, as he thought that since he was approaching his forties as a virgin, he must be something much greater than a mere wizard.
Great Sage 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.
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 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. Although it was finally able to answer questions, it remained passive and lacked ego: it wouldn't answer unless asked.
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 take 1 second and production of restorative items 3 seconds. Without the link, it takes 50 minutes.
- Thought: Raises thought-processing speed a thousand times. The speed of thoughts allows the user to analyze their surroundings for information in an instant and track the probability of an event by piecing together stored and acquired data.
- Analysis and Judgment: The ability to analyze and make judgments regarding a target. The ability to immediately know the solution to any problem they perceive and automatically formulate how to overcome any obstacle. User automatically understands the mechanics behind any issue or concept they perceive and know what must be done to solve any problem. Thus when a situation emerges the most optimal solution is automatically implemented
- Parallel Processing: The ability to perform multiple functions at once by allocating a portion of their mind to each task, for instance, to detach thoughts and analysis of phenomena.
- Chant annulment: When using magic, the chant is no longer necessary.
- All of Creation: The ability to comprehend any non-concealed phenomenon in this world. The user automatically analyzes and comprehends anything and everything they perceive instantly. The mind has unlimited storage capacity and is able to immediately recall any information stored with perfect clarity. The user continuously and without limit incorporates information gathered from the external environment. 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.
- Auto Battle Mode: By giving permission to Great Sage, one can let it control his or her body temporarily. In this mode, the mind is in a state of total awareness and reaction not impeded by higher mental function or emotion, more open and reactive to subtle sensory input, intuition, and spontaneous action. It is a mind that is totally calm - a mind not influenced or caught up in events or emotion, thus a mind more able to freely perceive and respond to any situation for the advantage of the user. Regardless of emotions, morals, or of what happens, the mind is only capable of cold flawless logical calculations and meticulous construction optimal strategy that will yield the most efficient results. They can adapt perfectly to all factors before they even appear, achieving maximum efficiency in the offense, defense, and strategy, ensuring optimal success as long as there is the slightest chance.