To get into the Mages Guild in The Elder Scrolls IV: Oblivion, follow these steps:
- Visit any of the seven Mages Guild halls located in the major cities of Cyrodiil (Anvil, Bravil, Bruma, Cheydinhal, Chorrol, Leyawiin, and Skingrad). Note that there is no Mages Guild hall in the Imperial City or Kvatch
- Speak to the head (guildhall steward) of any of these guild halls and ask to join the Mages Guild. You must have a clean criminal record with no bounty on your head to be accepted
- Upon joining, you will receive a Mages Guild Charter and a key granting access to most guild halls. You can then start taking on quests to earn recommendations from each guildhall steward
- To gain full membership and access to the Arcane University in the Imperial City (where you can do spellmaking and enchanting), you need to complete a unique quest for each guildhall steward and obtain their recommendation letter. These quests vary by city and often involve tasks like recovering lost items or investigating mysteries
- After collecting all seven recommendations, return to Raminus Polus at the Arcane University. He will officially advance you to the rank of Apprentice and grant you the Robe of Apprentice, giving you full access to the Arcane University and its facilities
In summary, joining the Mages Guild is straightforward-just ask to join at any guild hall with no bounty-but becoming a full member with access to the Arcane University requires completing recommendation quests from all seven guildhall leaders
