When you finish every Konquest mission, you get Blaze and Mokap. Nothing happens when you unlcok the whole Krypt, nor when you get all endings. The Final Secret hasn't yet been revealed, neither has the way of getting it. The most we know of is that it's accessed by pressing some button combination in some Screen in the game. We don't even know under which conditions (maybe we have to finish everything first, we don't know).