Yekop is one of the six new guardians that have taken the mantle of Guardians of the Universe, after Sinestro and Atrocitus killed the previous guardians.
Rise of the Third Army
For eons, Yekop and the other guardians were hidden and sealed as wardens in the Chamber of Shadows, along with Volthoom, the First Lantern, who they were assigned to oversee. When Yekop and the other guardians finally come face-to-face with their estranged siblings, they are shocked to see how emotionless the latter have become and briefly provide resistance, which results in one of Yekop's brothers being killed. They are again locked into the Chamber of Shadows until finally Simon Baz releases them.
Later, after Volthoom and the Guardians (save for Ganthet and Sayd) are killed, Yekop and the other guardians step into the role of Guardians of the Universe, though they relinquish their responsibility to Hal Jordan in order to experience the universe they had been earlier denied.
Yekop and the others begin playing a larger role at the end of Light's Out. After their voyage across the universe, they seem to have been caught up to speed on the comings-and-goings and are able to aid Kyle Rayner as both a white lantern and the host of the emotional spectrum's entities. With the end of Light's Out, they are seen surveying the wall that protects whatever is beyond the edge of the universe and become the only beings that know of Kyle Rayner's survival.