In the middle of doing the Mages College quests in Skyrim I noticed that my magicka bar was not appearing at all despite casting spells. I found that I could cast the Flames spell indefinitely without my magicka ever draining. I looked at my Current Effects and saw that I had three extra Magicka Regen bonuses, but there was no indication of where they had come from. So I was pretty much indestructible for the next hour of playtime or so before the effects wore off.
Where would these effects have come from? Would it have been anything to do with the Eye of Magnus (which I “Activated”), just a glitch, or something else?
The quest that gave you infinite magicka regeneration is Out of Balance
From the UESP site:
When cleaning the foci, a bugged two hour buff may be placed on you that increases magicka regeneration immensely. It is possible to get multiples of this buff during the quest. In the active effects category, it appears as “Fortify Magicka”. Selecting it reveals it as “Drain Magicka, +25 Fortify Magicka for 2 hours”. It doesn’t appear to increase magicka capacity at all (as listed on the skills screen), but increases magicka regeneration rate instead.
Some players have reported that the buff remains much longer than the stated 2 hours. In this case, the buff(s) can be removed by opening the character editor with the “showracemenu” console command (on PC) and closing it again. This will also remove other temporary buffs, such as blessings, and enchanted apparel will need to be re-equipped to restore their effects. (v22.214.171.124 of game)