I think we can go two ways from here. Lemme try the first [b]'[/b] 3 [b]'[/b]

Well, for how he gained physical form, that's thanks to the first person he met aboard the multidimensional vessel. The one agent that got killed? We'll call him Chekhov for now. He's a being that rules over dream, you can say. Sadly, because Chekhov was killed by that one Shadow Eternity member in that one attack, even Bass has yet to understand how he's "outside" of the net. Chekhov's role will be expanded upon in the storyline. And... so will the Shadow Eternity member, whom Bass fought to the toenail for a standstill. It left, but the blood-lust and level of challenge amazed Bass. He came to the conclusion that there was no worth in UMMA, if even a non-agent could stand up to something an agent could not. Instead, he set his sights on Shadow Eternity. There was great destruction to be doled out, he knew. However, if he acted alone, it could be harder to encounter these Shadow Eternity operatives, and even harder still if UMMA stood in his way. To make things easier, he decided that he would play along with the UMMA for now.

However, I want to say that these are the reasons only at first. There could be more reasons for why he agreed to joining UMMA, reasons rooted deeply within. We'll just have to see, eh?

On the administrative side, it has to be understood that Bass.EXE and Megaman.EXE (the blue bomber) are currently the two most powerful beings in their universe. Because his extraction took place immediately during the storyline of [url=http://megaman.wikia.com/wiki/Mega_Man_Battle_Network_6]Megaman Battle Network 6[/url], administration of the UMMA - could've - come to the conclusion that Megaman.EXE needed to be left to be able to handle problems back in his own universe. So they turned to Bass.EXE, whom must be mentioned to have not been created with his darkness, but rather, was forced to nurture it in order to survive after he was wrongly accused and betrayed.