The Atronach Stone (Skyrim)

The Atronach Stone is one of the 13 Guardian Stones located in Skyrim. The Atronach Stone gives the player a large magicka boost (50 extra points) and enables you to absorb spell damage (50% extra absorbing). However, it causes the rate of magicka regeneration to decrease (50% regeneration decrease).

Location
The stone is located between Windhel and Riften, in the marshland, just outside the mountain range between the two locations. Near the Eldergleam Sanctuary and Darkwater Crossing, the stone is by the river to the East.