Scroll of Upgrade
Warning: This item has a short shelf life.
The Scroll of Upgrade sprouts a 20-minute timer above it as soon as it is picked up. Reading it upgrades one random item among those currently equipped, and by its own description the upgrade could be small or it could be huge.
The description pitches it as improving something already comfortable instead of getting something new. Stripping off every item but one, so that the upgrade lands where it is wanted, can be done, though someone who has seen people try it advises against it. By that same account, items like this expire quickly so that nobody can hold one back for a much deeper level, where it would be worth more than intended.
How far into Dungeon Crawler Carl have you read?
Set your place and this page rewrites itself to exactly that point. Nothing ahead of you will show.