I had to use the console to unlock it again. Not only that, but if you close the vault doors, they re-lock themselves and become unpickable. The only thing you can really use for storage (without manually picking up and dropping things into the existing chests) is a barrel. I just fired up the game real quick to confirm things and my original guess was correct. Story wise, it would make more sense that the mages guild holds the largest library.

Or you could instead make an addition to the college of Winterhold.

It'll probably have to be a mod you enable AFTER you finish the guild's quests otherwise when Vex and others open it, they'll find it full and proclaim it empty.ĮDIT: I should mention that if you include several bookcases, you'll want to make the vault MUCH larger. I'll become Guild Master soon so I'll be able to verify whether or not it stays empty, but if it does stay empty, I hope someone like yourself makes a mod to change that. With that said, your suggestion of being able to use the treasure vault as a storage and display area is BAD ASS. In my mind, I came into wealth because of the Thieves guild-I have no problem giving back. I'm fairly wealthy now and have two homes so I don't really mind how I spend my money. I've started piling gems, rings, necklaces, weapons and armor into the open chests. I finished the Thieves questline minus becoming a full fledged Guildmaster, but I have wondered this as well.

Skyrim thieves guild safe storage