There are thirteen magical standing stones in Skyrim. Each of them is carved with a different star constellation. All of them grant some form of bonus but some bonus are accompanied by penalties. One may accept the power from any stone but one can only possess the power of one stone at a time.
The standing stones are usually alone but three of them can be found together. These three stones represents the three basic archetypes of the adventurer; the warrior, the mage and the thief. J’Zhirr came across them when he was fleeing from Helgen.