We know what two artifacts were required for the Player, but which ones did Mankar Camaron use? I can imagine Dagon would have willingly given him some of his own blood, or perhaps Camaron used another of the Artifacts besides the one the player used (I'll call it a game mechanic if anyone mentions the fact the player can still own all of them despite this hypothesis). What's really a good question is where would Camaron have gotten the blood of a Divine? What constitutes a Divine, anyway? Apparently it doesn't have to be an Aedra, because Talos was a mortal who only became a god AFTER death. Unless his blood also changed when his soul did, that was simply the blood of a mortal which Martin scraqed from the armor.
The armor was still in Sacre Tor when the Champion is asked to retrieve it, so apparently Camaron had not been there or used that blood. Where in the world did he get the blood of a Divine? Another artifact such as Auriel's Bow perhaps? Do we know how Aedric artifacts are even made? Perhaps their creation mirrors the process of Daedric Artifacts?
And finally, as a last part, as an interesting little scenario:
While they weren't shown bleeding per se in the game footage, both Dagon and Akatosh received several nasty mortal wounds during their brief duel. Realistically, both of these living breathing creatures would bleed when damaged to this extent. I would imagine their blood fell to the streets in copious amounts. This would mean, besides its sheer value in gold, a very powerful substance or substances were left behind from the failed Invasion - the blood of gods. Who knows what insane alchemical properties this blood might posses? It's been suggested before that perhaps all gods bleed Ebony, but that's just one theory. We know that's what Lorkhan bled but were we ever given true verification that Daedra and Divines have Ebony for blood? If not we could imagine that two separate but powerful substances were spilled that day, which were no doubt collected by the Legions for the Imperial Battlemages or some other elite organization to study and preserve. And perhaps to someday be used to open other portals, if the barriers should ever weaken again...