In the final mage quest (the Eye of Magnus), I was expecting the fight of my life against Ancano. But I kept getting the message "Activate the Eye". I wasn't sure whether I'd done it or not, so I just kept using the Staff of Magnus trained on it. Finally, I turned around to see what was happening, and I found that Tolfdir had killed Arcano all by himself! So of course I took him to a local pub and celebrated his victory with Honningbrew Mead, roast leg of goat, and lots of dancing and loud laughter. At that point I wished I had installed the mod that let Tolfdir become the ArchMage instead of me.