Eternal Guardians, Dark Horadric Constructs are a pair of Super Unique Sand Dwellers assisting Zoltun Kulle in battle with the Nephalem in Diablo III.
They do not have any special skills, but are very tough and deal great damage in melee combat. Upon death, each of them drops a Health Globe.
There is an achievement for killing Zoltun Kulle without destroying his Eternal Guardians. They die immediately after he is defeated, though.