Obtain a Spool of Thread and the Doctor's Cleaver, then take them to the Sanctum of Reanimation Slab and use Olakin's remains to attempt to reanimate the crusader. Return to Darkrider Arly at Blackwatch when this task is complete.
We can't afford to waste any time putting Olakin back together. Fortunately, the Scourge has provided a perfect place for you to stitch him back together.
Near the Fleshwerks' flesh giant lab is the Sanctum of Reanimation. Search the area for a spool of thread and the doctor's cleaver. Then, take Olakin's remains to the large slab in the middle of the sanctum and get to work.