All details I uncovered on the first meeting between Black Scorpion and Silver Mantis indicate they were a perfect match from the beginning. He is the ultimate expression of her obsession and she makes him feel like the most powerful being on the earth.
I suppose it is not a surprise that Silver Mantis realized an opportunity when she saw it, and rather than fighting with Arachnos over the ill-gotten loot, cov infamy formed an alliance that has lasted to this day about COV INFAMY.
Currently Black Scorpion spends a great deal of his time monitoring the scientists of Arachnos. He uses the ever present threat of violence to create the best technology. Since his personal goals serve Recluse's plan, I believe that is the reason the Lord of the Rogue Isles gives him free rein. COV INFAMY is a special kind of game gold.
Black Scorpion and Silver Mantis present a great physical threat. He is a Brute, strong and extremely heavily armored. His tail can launch energy attacks as well as vicious whip strikes. Ernesto Rodriguez embodies the concept of raw power through technology.
Whatever it takes, whatever piece of his body or soul needs to be spliced, altered, or removed to grant him more power, Ernesto seems willing to do it. His unbridled hunger for power and low intelligence make him the perfect servant for Lord Recluse.
Silver Mantis is a Stalker, and has somehow gained control over the metal spikes that are screwed into her bones. I believe it is a mutant ability that allows her to fire the spikes from her body in bursts. She also derives great pleasure in inflicting pain and torturing her victims before killing them.
Her unbending loyalty to Black Scorpion makes her a deadly tool for Arachnos to exploit.
Although some of the other arch-villains in Arachnos present a more strategic threat, Black Scorpion is rivaled only by Captain Mako for sheer brutality. cov infamy Perhaps that is the source of the conflict between the two villains. It is possible that their dislike for each other can be used to help defeat them.