[BewareTheBarnacleGoose]

This is an interesting question. The wiki mentions that poison damage does not trigger BV, so you could throw a horde of milita (atlantis has poison spears), cast Antimagic to reduce the chance of BV, and hope that a couple make their saves, and cause some extra damage from poison. The wiki also says that Paralyze does not trigger it, so you could try spamming it, although the Vastness' MR is very high. If it has been GOR'd, then Magic Duel will work too. Unfortunately, any of these strategies force you to loose much more resources than your enemy, so it's a sort of a phyrric victory for you...

Of course, someone more clever than I probably has a better way...