You can find Grand Soul Gems in Oblivion at several guaranteed and possible locations:
Guaranteed Locations for Grand Soul Gems
- Arcane University :
- Three Grand Soul Gems inside display cases in the Arch-Mage's Lobby (behind a Very Hard Lock)
- One in the Mage's Quarters (also behind a Very Hard Lock)
- Chorrol Mages Guild :
- Two Grand Soul Gems in a display case on the main floor (Very Hard Lock)
- Three more in another display case near the front door
- Crayfish Cave : One Grand Soul Gem
- Drakelowe : One Grand Soul Gem in the basement (secret fireplace entrance)
- Nornal : One Grand Soul Gem on some ruins west of Drakelowe
- Squandered Mine : One Grand Soul Gem behind a hidden door on the lower level
These locations reliably contain Grand Soul Gems, but some require picking locks or defeating enemies to access
Possible Locations (Less Guaranteed, But Worth Checking)
- Imperial City Market District : Buy from merchants Aurelinwae and Calindil at the Mystic Emporium
- Mages Guild Halls : Merchants often have Grand Soul Gems for sale, inventory refreshes over time
- Ayleid Ruins : Search Ayleid casks and containers
- Dagon Shrine Living Quarters : Occasionally spawns in a chest during the Mythic Dawn infiltration quest
- Random Loot Drops : Spellcasting enemies often drop soul gems, including Grand Soul Gems at higher levels
Waiting for seven in-game days resets merchant inventories, allowing you to check for new stock
Additional Tips
- Grand Soul Gems spawn more frequently as your character levels up, typically starting around level 17 to 20
- You can farm soul gems by repeatedly entering and exiting certain dungeons with chests containing soul gems, then waiting in-game to reset the loot
- The quest "Sins of the Father" also provides multiple filled Grand Soul Gems during its progress
In summary, the best method to find Grand Soul Gems is to loot the static display cases at Arcane University and Chorrol Mages Guild, check merchants regularly, explore certain caves and ruins, and farm chests in specific dungeons after reaching mid-level character progression
