So what's the rationale for people thinking it's a reasonable idea to try to gank Eshin's sorcerer? It seems like an unnecessarily risky proposition.
The skaven sorcerer has been fighting for more than five hours, and all the skaven had popped their black hunger rush around five hours ago.
The black hunger thing is like a super soldier steroid or adrenaline rush or whatever, but the jist is that it gives the skaven a large short term boost to their combat prowress.
After it ends, they go into a freeding rampage where they desperately try to replenish the energy that they spent eating anything they can before they drop dead of starvation and even when they do eat enough they are exhausted.
So, do we want to kill an exhausted skaven wizard who has been casting and fighting for more than five hours and is in "Black Hunger Recovery" or has had to fight Mor rats who where using black hunger as it was desperately fighting them while we are fresh, having spend only an hour playing "terror in the night" and the rest in one place acting as leading Thane? Or would we prefer to let him leave and recover from all this before he returns with a lot more of his "Friends" to get at the mountain full of warpstone that they covet oh so greatly, maybe try to take the eight peaks for themselves again?
I mean, we literally have a giant mountain of stuff that attracts skaven like gromril does dwarves, he is not going to leave and never return anymore than chaos will never return to ravange the lands. He might leave for a time, he won't stay away.
Best take him, and the other skaven out here rather than keeping them around, wanting our stuff and leading a horde of new fresh chaff to steal our Karak with.
Edit
The rat has been fighting and casting for hours against an almost equal force as they both use black hunger to try and overwhelm the other and prevent their opponents from beating them.
He uses a unrealiable and exhausting Dhar based spellcasting system and is probably running off of warpstone based drugs, willpower, fear, the bodies of dead skaven and the Hope of victory being dangled infront of him.
The only way he could be safer target is if he was a paralyzed from the neck down, stripped from all of his gear, has the been examined on a surgons table for anything in his body, his teeth pulled, so drugged up that he is oblivious to everything and is in the mouth of the Hysh Ice Dragon who is preventing it from even starting to cast anything.
That is the only way I can imagine him being more vulnerable than he is now....
Plus, he is currently pinned down in a general area so it will be relatively easy to find him. "Dhar Battle Magic" is not hard to notice, and neither is a skaven jumping in and killing Mor clanrats with spells and blade before running away.
Later, and we wont have more than a hint of an idea of an intuition of where to start looking, unless he miscasts and pops like a dirty redioactive bomb of Dhar or until he kills/tries to kill someone.