Diablo 2 Resurrected Cairn Stones are easy to find, but tough to activate.
Before you can do anything with them, you’ll have to take on another unique boss and learn the secrets of the portal they guard. Fortunately, everything you need is fairly close together.
The Search for Cain quest tasks you with finding six Cairn Stones in the Stony Circle, then activating them in a specific order to solve the puzzle. Getting to the Stony Field and actually activating the stones is a bit of an ordeal, though.