A few weeks back I was reading through the Dungeon Master’s Guide and I looked at the picture of the bag of devouring. Both bags in the picture are really quite mischievous looking. That is when I thought… what if your bag of holding spit out the item you need some of the time… what would happen the other times? Enter the robe of useful items.
When retrieving an item from the bag of unreliable holding (which acts as a bag of holding usually), there is a chance you instead draw a random item (use the table from the robe of useful items). The bag is then unusable until the next dawn (you cannot retrieve items or draw a useful item until then).
Obviously, I have not worked on the text wording, but you get the picture. I figure between 10% to 20% chance the bag activates. I really just liked the name that popped into my head and I wanted to use it for something.
But… what do I know…?