Alright, starting with the 3 Warhammer 40k tags, we have:
warhammer_40000
warhammer_40k
wh40k

These are all aliased to the warhammer_(franchise) tag, but they shouldn't be. 40k is a branch of the Warhammer Franchise, not the franchise itself, so the 3 tags listed above should be aliased to eachother, de-aliased from warhammer_(franchise), and then implicated to warhammer_(franchise).

Then we've got warhammer_fantasy, which should just be implicated to warhammer_(franchise).

Also, skaven should be implicated to warhammer_fantasy.

That should keep skaven from popping up when you type in "warhammer_40k", and make the Warhammer franchise tags nice & tidy.