Those ones seems to appear at every page, eating page space and filling wiki with mostly useless random informantion. Can i kill them all at once?
You can't. That involves modifying the sidebar, which Wikia doesn't allow.
Ok, then... can i at least change it contents to something like navigation links or something?
No, I'm afraid you can't.
Uh. Im really angry about this.
If I remember correctly you can remove it, but only for yourself. You can give the code to remove it to other users so they can use it.
However you cannot add it to a wiki's css.
Yeah local CSS is really cool, but of course its not a solution to users that would come to wiki for a 2 minutes to just see some ingame item or monster. They would not even register. But i suppose that they wouldnt be happy to see pages like http://ru.kung-fu.wikia.com/wiki/%D0%9D%D0%B5%D0%B9%D0%B3%D1%83%D0%BD?direction=prev&oldid=1371 when the text area is about 400 pixels.
What do you think?