I'd create the BLACK NETWORK ASSET
A skilled assassin rogue who works for the Zhents but only shows up when things really go bad
He appears behind the commander of a Zhent outpost and is like "I'm here to fix what you screwed up, get your thumbs out of your asses"
And he gives long monologues when he kills nights, saying things like "You learn how to fight from some old man in a castle?" then he kicks dust in the dudes eyes and hamstrings him or something, I dunno
And he analyzes the art of his enemies to learn their weakness
And he's really into caligraphy
...
On second thought that's terrible but I type it all out already