[quote=@Doc Doctor]
<Snipped quote by MelonHead>

Whomever you want to fight Shash with is fine, tier doesn't matter.
[/quote]

Well, I'd prefer to fight with Higan for story reasons, but he'd be a difficult opponent for your character particularly as one could argue walker mechs in a fantasy setting are pretty much designed as a counter to scary organic monsters. If you think you can scale your monster appropriately to face down the ASP then we can go with that, in the current format the Clockwork Man would probably be a fairer fight (In his weaker form, First Arc) but not necessarily one that would make sense, as neither character would have all that much interest in the other. 

Also, I'm fucking excellent with the Clockwork Man, which is worth considering. Probably my best character in regards to my preferred play style. 

To be fair though, I am a little hazy on what biological properties your bat-snake-xenomorph actually has. Does it have organs, bleed, breathe? Or does it literally just have to be blown to pieces in order to die?