I just re-watched a couple of Sailor Moon episodes while working on this piece. It's been ages since I've seen that show and had completely forgotten about these baddies.
Ann and her brother Ail (put 'em together and it sounds like Alien) are the last of their race. The two went undercover as human siblings on Earth where they have an evil tree that steals energy. No matter who the enemies in Sailor Moon were it seemed like they always wanted to steal energy, either from a kooky computer programs or evil gyms.