Stone Guardians
There are thirteen standing stones (large patterned stones standing vertically on the ground) scattered throughout Skyrim. They provide two achievements: finding one and receiving its blessing and finding all thirteen (but for some reason, I was given one for 10; there is a suspicion that another value is counted for the achievement, either including something else, or due to a bug some stones are counted multiple times).
Each stone grants a blessing (to receive it, approach the stone and press the action key), and you can only be blessed by one stone at a time (previous effects are removed).
Below I will describe the effects and locations of the thirteen stones. Photos are attached. Don't forget to use the compass at the top to accurately find the next stone.

The Thief, Mage, and Warrior Stones


Location. Southwest of Riverwood and northwest of Helgen, by the river at the bend in the road.
The Ritual Stone


Location. East of Whiterun, on a hill, on the southern bank of the river. About midway between Whiterun and the Valthume Towers.
The Atronach Stone


Location. A group of stones west of the Misty Crag. You can also head east-southeast from the shrine of the Great Tree, which is in the swamps between Riften and Windhelm.
The Shadow Stone


Location. South of Riften, on a hill.
The Steed Stone


Location. To the west-northwest of Solitude, north of the Wolf Skull Cave.
The Lady Stone


Location. On an island in the lake west of Riverwood.
The Apprentice Stone


Location. South of Solitude and northwest of Morthal, on one of the islets.
The Tower Stone


Location. Halfway from Dawnstar to Winterhold, on an icy cliff by the shore.
The Lover Stone


Location. East of Markarth, on a mountain by the river. I went west-southwest from Karthwasten, I had to resort to climbing with my trusty steed and cross two mountain ranges. You can also get there from the river, in principle.
The Lord Stone


Location. On the northern peak of the mountain range (stands out in height relative to the surrounding terrain) southwest of Dawnstar. You need to approach it from the east, and you can head directly west from Fort Dunstad.
The Serpent Stone


Location. Almost directly east of Winterhold and significantly north of Windhelm, you can find the wreck of "The Pride of Tel Vos." East-northeast from there, there will be an iceberg with the stone on it (there is a whole cromlech, visible from the sea). From the crash site, the stone marker should already be displayed on the compass.
When creating this post, I referred to the guide: Skyrim Standing Stones Location Guide.
The preparation of this post used [post]Offline post editor for Gamer.ru [ver 2.6.3][/post].