I think Wolfbode mystmountains are the easiest of most - since their army usually consists of low level mounted troops armed with blunt weapons - so casualities going to be minimal anyways (I got 150 injures and only 3 death in my last battle with them - and only cause I've run out of arrows and still wanted to get 50 renown for the battle).
Btw, there's also Drunken Captain - von Brouhaha - which is easy as pie since he leads an army of peasants mostly.
The only problem is that he spawns too rarely and don't last long, since AI lords wipe him in days.
P.S.

I have a question about Syla's name (Syla Uzas) - since it can be translated from russian like "Horrific Force" - so I wonder if it was made for purpose?