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[2e D&D] Before Karsus, was magic capable of reaching arbitrarily high levels, or was level 12 the limit?

Ok, so what we know:  The god of magic USED to be Mystryl until Karsus cast the first and last lvl 12 spell, "Karsus's Avatar", which kills a god and gives you his/her power.  After Karsus was defeated (or in the process of defeating him?) Mystryl reincarnated into Mystra, who rewrote the laws of magic putting a hard cap on magic: no spells above level 9 ever again.

My question is... before this hard cap was established, was there a limit?  I mean, the Karsus's Avatar spell was the highest level spell ever *actually cast*... but assuming an alternate reality where that never happened, could someone else have developed a level 13 spell?  Level 14?  Level 100?  Level 1,000,000?  Level {arbitrarily high}?

Additionally, is there any way to theoretically discuss what magic of a given arbitrary level would be capable of?  I know 3rd edition's Epic Magic system tried to codify it, but I don't think it matches what we see 10th and 11th level spells do.  Here's all the 10+ spells for reference.

***Level 10***

**Lefeber's Weave Mythal** - Create lvl x 300' sphere, *perfectly* impenetrable, even by wishes or divine intervention, unless you have the key.  You can also make it auto cast other lower level spells on anyone attempting to enter WITH the key-- the spell descriptor suggests lightning bolt for some odd reason, but I'm thinking things like Domination or Gaes/Quest would be more useful...

**Mavin's Create Volcano** - As name implies, create an active volcano somewhere within (lvl) miles of you.  Also creates earthquakes as a side effect.

**Mavin's Earthfast** - Makes stone indestructible for (lvl) years, useful for making cave-in proof tunnels, city walls, or just buildings that don't deteriorate.  Area of effect is (lvl) miles.

**Proctiv's Move Mountain** - Sever a mountain from the ground and move/rotate it wherever/however you like. Once you're done moving it around, you can just leave it hanging there floating in the sky.  Permanently.

**Tolodine's Killing Wind** - Kill *everything* within lvl x 300 feet of you (or from a point within that range, extending your potential reach to double that in one direction).  Living things do get a saving throw, but you can set the DC of that saving throw to be more or less as high as you like... it's just that the stronger you cast the spell, the more likely you'll get *yourself* sucked into the Negative Energy Plane, unable to be resurrected.

**Valdick's Spheresail** - Permanently imbues any vehicle with the ability to fly at what is, as far as I can tell, at or near the speed of light, and specifically mentions that it's useful for either interplanetary travel, or being functionally equivalent to a teleport spell to anywhere on the planet.


***Level 11***

**Mavin's Worldweave** - Permanently alter the weather within (lvl) miles of you.  Extreme alterations of climate possible with multiple castings of the spell (eg, Arctic to Tropical takes 4 castings).  As far as I can tell, there's no real cost to casting it as much as you like, so this limitation may as well not be there.

**Proctiv's Breach Crystal Sphere** - Can be cast to permanently seal an entire plane to planar travel, or cast again to unseal it.

***Level 12***

**Karsus's Avatar** - Kill one god located anywhere in existence.  Assume slain deity's power.  It's unknown if target god gets a saving throw or not, whether the god is aware of you casting it during the 6 hour casting time or not, or if any other factors apply.
gpt
It is unknown. There *may* be some beings or intelligences that may know, or even be able to attempt it, but ultimately this is not general arcane knowledge. Please keep in mind, Elves have always been able to--and still may--cast "high" magic which is the equivalent to level 10+.  

It should also be noted that nearly all the magic that the Netherese practiced--including that of Karsus--ultimately came from the Nether Scrolls. The real name of the scrolls, however, was *The Golden Skins of the World Serpent.* The scrolls were an artifact that was created by the first of what the elves called the *Iqua tel'quessir* or the *Creator Races*: the Sarrukh. That means the Sarrukh were capable of practicing magic and crafting spells of similar likeness. Since this happened before common recorded history, it's difficult to say with certainty whether or not the Sarrukh (or the other Creator Races that came after them) practiced similar spells. We do, however, know that there were flying cities in this time, long, long before there was even a Netheril.  

There is also evidence that magic back in the Days of Thunder was much less regulated, possibly because Mystryl had yet to assume a more coherent form. If you go back far enough, the only gods that existed who exercised any authority were Selune and Shar, which means that the Weave may have been completely unregulated at some point. Mystryl may have been formed out of recognition that in order for the universe to form further, regulation of the Weave would be needed, and thus would justify the existence of a god to do so.