Dark Horizon, released as Tarr Chronicles: Guardians of the Border (Russian: Хроники Тарр: Стражи Пограничья) in Russia, is a space combat simulation game developed by Russian team Quazar Studio and published by Paradox Interactive.

The game takes place circa 100 years prior to Tarr Chronicles.

The game is set in a fictional galaxy called Enosta, which is under the invasion of a malignant entity simply known as the Mirk.

The player is a member of the Guardians, a society of people partially infected by the Mirk, who are attempting to construct a structure to contain the entity from wiping out rest of the galaxy, called the Light Core.

The player is assigned to defend the Guardians from attack from the Mirk and ultimately finish construction of the Light Core.