Becoming best friends with the Dark Elves will probably only work out if we glue at least three more rows of spikes to our pauldrons, based on how villain characters get the immunity to ambient backstabbing and all, but we don't really need to be friends with them in order to profit here:
Mathilde kept asking about how she could get the Dark Elves to stop killing Imperial people. Not for forbidden knowledge or baby wine, just a cessation to hostilities. That's not really a morally dubious deal, and it's eminently defensible even in a spiritual context, much less a utilitarian one. Our citizens dying is bad.
If we can negotiate a halt to Dark Elves murdering people for any length of time, even if it's just a Dark Elven ruse while they scheme about something else, that's still time they spent not murdering people. It's still a win. "Surprise, we're still evil!" doesn't hit as hard when you only go in with the goal of getting them to pretend to be 'good' for a while, because you still got that while out of them.
We can have a lot of OOC arguments about them being a challenger for the throne of 'worst people in the setting', but in practical, vote specific terms, where would we be going wrong? 'Maybe stop killing us' is pretty tempting. 'We should let them keep killing us because otherwise we might not hate them as much, which would be worse' is probably true, but very unpalatable, you've got to admit.
Forbidden knowledge isn't even really on my mind, anyways. Nagash already got everything important out of them that Ulthuan wouldn't give us, and we're pretty far along on collecting that sort of stuff.
