They're mainly intended as antagonists, but you could do a Drakh game if you wanted to. They are probably incompatible with a normal B5 party, in terms of both power and outlook.
'Hi, I'm Bob the Trader. This is my pal Ted the Telepath, Ruthal the Ranger, and this is our new friend, the Drakh. He's poisoned us all and put brainworms in our ears so we must serve his diabolical plan to bring down the Interstellar Alliance out of misguided revenge for the loss of his false gods. How're you?'