Face palm.... thanks dhope. How did I not see the animal? Very much overthinking. I was convinced there was an ancient obscure word for vampire that I didn't know.
20a/24d - 2 letter "soldier" (US) + 3 letter "soldier" (insect) then scond word is 3 letter "overtake" (think 'athletics') goes around E(uropean) - definition is "monster effort"