[Norfleet]

Yeah, I kinda discovered this by accident also.

But vampires are probably perfect for the job: They fly, so they can strike instantly. They're undead and immune to cold and poison, just as the queen herself is, so none of the damage shields that the queen could use, if she Lasts that long, will affect them: Breath of Winter is useless. Soul Vortex is useless. Fire Shield doesn't do enough damage to stop the vampires from regenerating it back. Astral Shield will only slow the effect down.

What's more, if you are counterattacking with the vampires on YOUR dominion, YOU RISK NOTHING!

Of course, for a non-blood nation, vampires may be difficult to access, but surprisingly, you don't need very many. I was sunk by a mere 17 vampires, managing to slay only a dismal 4. That amounts to less than 3 castings of Blood Rite, a sum of a mere 78 blood slaves.

Even if you don't want to go the blood route, anything similar will do: Ghosts, for instance, can accomplish the same effect, although you will not be able to fly-attack....unless you use Mass Flight. Mandragorae could probably do the job, but their sleep vines are slightly different from the Life Drain attack shared by Ghosts and Vampires, so they may not produce the same result....but they're much cheaper and more expendable.