There should be a scenario for this. I think it should be like a super powerful Rune in the middle that's worth the majority of your victory points so people don't just ally up and crush one person, or one person doesn't sit back (I mean let's be real, I'm still gonna sit back with Aliana and dial in that late game damage) and wait for others to weaken themselves.
Would be cool thematically too, like there's too much terrain for the rest of the armies to advance on this ultra powerful artifact so the heroes have to enter and duke it out.