Lockpicking

[Pixelclicker]

although I love thieves it would make them a tad bit OP - nothing would be safe

I disagree with this proposal.  The magic-locked box as it works here and in-era doesn't protect invis and reflect items and most weapons.  More importantly, it doesn't protect ANYTHING if it's not carried or not locked - which is still what most people do b/c locking and unlocking a chest constantly to get stuff in and out is a bit of a PITA.

It's a reasonable countermeasure against someone risking nothing other than a rune and a recall scroll, and it doesn't happen automatically, it requires the user to expend effort and resources.