I found a Murmur during the unicorn event. It's quite good, but unfortunately I have a physical mech.
Hurlbat is pretty bad. It's closer between Void and Greedy, but I think Void is better.
In 5 turns, if the drone attacks once per turn (assuming 2 other physical hits per turn for simplicity), Void does 352.5 more damage, which needs to be overcome by Greedy's extra -5 armor. Under these assumptions (if my math is right), Greedy does +0, +15, +30, +45 and +60 extra damage per turn. That means in 5 turns, Void still does 200 more damage.