I would suggest that you play Vanar, but seeing that you have that part down already, I would say just Jund them. Jund 'em is always the answer.
In all seriousness, your play really depends on which Vanar deck you are playing. If you see them drop Metalurgist or Kujata, play your minions (preferably snow-ball minions) near the back. Then, their Slasher will just be a large body that Vanar has plenty of ways to deal with. If you’re playing Arcanyst, this would be a good time to play Circulus or Owlbeast out of reach. If you’re playing Vespyr, you can take this chance to play Glacial Elemental. If you’re playing aggro… there’s not really anything to do. Maybe Remove the Kujata? Ignore it and go face?