Aftershock (Radiant) quest - how does the Staff of Magnus fit in? Does it have a special function in this quest?
Solution 1:
The odds are pointing towards no. On the Quest Stages page, it doesn't mention anything about the Staff of Magnus being used for anything (besides his recommendation,) just the Eye. If it really was crucial, it would have been listed on the Quest Stages page. Also, if you can drop it, it's not a Quest Item. And that it has monetary value will only further confirm this.
Granted, because he recommended it, it would probably make the quest go faster. But because you already finished the quest, I'm not sure how this would benefit anymore.