The Prism Stone is an interesting game item. They can be used like bread crumbs to keep track of where you have been. Simply drop one and it will glow one of eight colours.
The in-game description mentions a rare colour, but some independent testing appears to show there is no colour that is more rare than others.
You can also drop a Stone off a ledge. If it breaks then the drop is too far for you to fall.
Snuggly the Crow will be happy to trade one for a Demon Titanite. This makes for an extremely good trade for you.
Where to buy one
The Undead Female Merchant or Patches will sell you as many as you would like for 10 Souls each. You can only carry 99 at a time.
Undead Female Merchant, safe behind her bars.
- Keep track of where you have been.
- Test if you can make a drop safely or not.
- Trade one for a Demon Titanite.