I didn't object to the match between Shady & Mon, just the way she subjected herself so completely to him - not that he showed any indication that he expected this behavior. Now I know there are plenty of relationships like this is reality, but it did not ring true to me that someone raised from birth to be a warrior and a Planetary Champion would lose her self in anybody, even a legend like Valor. She basically gave up her life, did the nun routine and abrogated all her responsibilities after his death. For years after his death - and this only ended when he came back to life.
Personally, it might be a nice fantasy to have someone so devoted to you that they can't live without you, but it's kinda unhealthy too. After Valor's death, I would have had Tasmia turn a little harder, angrier, a loner - but still out there fighting.
In the current story line, I agree she would eat someone like Lyle or Garth alive. They'd probably avoid her like the plague, maybe they're even scared of her in the way that you momentarily freeze when someone really unpleasant comes after you (usually to give you shit about something). She probably doesn't even know someone like Brainiac 5 is alive.
Tasmia and Val could be interesting, in that he would appreciate the warrior ways but could provide some calm and meditative balance. Teach her a few things and he wouldn't put up with any b-s either. She could have a lively relationship (not necessarily romantic) with Wildfire also - there's a guy who can give as good as he gets, mouth-wise. Yet he doesn't seem to have the anger that Umbra has.
Another (poor sap) match-up would be Timber Wolf. He's tough, he's a fighter and he falls for the wrong girl. It would be tragic, but possible. He would be too nice, try too hard to please and would never be good enough for Miss Planetary Champion. (Actually, I think T-Wolf deserves a break this version.)
