morningbus
Serious Sam is a wicked gahbidge series for chowdaheads.
So why is Oliver going back to Slade? To help him finish Chase?
The finale isset on the island. Seems like Chase has been abducting people close to Oliver and keeping them there. When you're up against a foe, on an isolated island, who's prepared for any reasonable thing you might do... who else can you can call but one of the strongest fighters in the world who's already secretly there and waiting?
And, I think in terms of strategy:
recruiting Slade is a move that Prometheus probably hasn't accounted for.