This is Alan and Ann. They came from a far off planet with the Doom Tree seed. The seed emplanted itself into an apartment building. Alan and Ann took up residence there, so they could feed the Doom Tree. The Doom Tree feed off energy. They transformed themselves into two High School students, so they wouldn't seem out of place. And so they could find energy for the Doom Tree.
They used monsters called "Cardians" to help them take energy from humans. They gave the energy to the Doom Tree so it would live and in return, they would live. Though they tried to feed it energy, the Doom Tree started to wither and die. They lured the scouts into the room where of the apartment where the Doom Tree was. It started to gain some energy. But, as always, the scouts defeated them and the Doom Tree.
They learned that the tree needed positive energy, not the negative energy that Alan and Ann had been feeding it. They felt so ashamed that they had been the ones hurting the "Tree of Life" as it called itself, that they returned to space, creating their own, postive love energy to keep the tree alive.
