system
Given the following post, respond as if you're commenting on Reddit:
human
[TES] What is the upper limit of magic? Is Shilandor the strongest mage in history? Are there distinctions between witches, warlocks and mages? Are there any races that simply can't use magicka?
gpt
Well the Dwarves used magic polished to such a degree they called it a science, Tonal Architecture, and used it to create metal frozen in time so it never decays, puzzles that could trick "gods" like Azura, and, y'know, the Numidium. That last one is probably tied for strongest thing on the physical world. While the original needed the Heart of Lorkhan to function, Zurin Arctus retrofitted it to use a soul gem with a reincarnation of Lorkhan trapped inside. It basically gives Akatosh the god of time a swirly every time it's turned on. This thing screwed up the time and the universe so badly that it's technically *still* fighting the war it was brought back for in other dimensions. It also forcibly ascended at least 2 gods, with one of those being a contender for capital-G God, since he is technically Lorkhan reborn, and Lork is the soul of half of the original Godhead who created the universe. 

So that would make it seem like the upper limit of magic is that there is no limit, as long as you know what your doing. This tracks with what we know in lore. Magicka streams in from the Sun and stars, which are holes into Aetherius, a realm of infinite energy and possibility. Tonal magic isn't quite the same thing, since it doesn't use magicka. Skyrim shouts don't deplete your mana bar when used for example, but they are much much less complex than dwemer tonal architecture.

I vote the Numidium as the greatest extent of magic seen.