Harbringers are amazing. I've only tried them out in SP, but they've got flight, great Air buffing potential, good HP, can bless themsleves, brutal precision, and absolutely fry demons/undead with their built in massive area ranged attack. Just 25 gems a pop, and Conj 6. Have to be Pythium or Marignon though
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Mictlan Tlahuelpuchi cost 25 blood and are Blood 6. I like to send them out with just a regen ring, a bane venom charm, and some blood slaves. They can fly into an enemy capital, turn into a super-stealth dog and disease it for a while. When you get Blood 7, assassination using Leech is very effective.