Evergreen is inherently cautious (different angels have different personalities, of course), and is inherently worried about setting bad divine precedent. Frankly, he hates this entire situation. He's been dragged into what the Gods shouldn't have touched in the first palce, he thinks, and now he's almost certainly going to be asked to give his life for the cause; if Imbindarla's four servitors react to what's going on around them, he suspects that they'll concentrate on the servant of Galanna, since She was the one who killed Imbindarla.
In other words, he's interpreting divine stricture more conservatively than some other angels might.
It isn't cowardice by any means; more a concern for his place in the world to come, and what would happen if he falls here. Since he gets eaten by Elder about six rounds from now, one might argue that his caution is well-founded.
! I hope he and his wife get some sleep...we are a little bleary-eyed these days since #2 arrived a couple of weeks ago.
