Evolutionary arms race

The "Arms Race of Evolution" is a euphemism for the evolutionary competition between two previously-cooperative species. It began on a distant planet, eons ago. One species resembled an Earth frog, and one an Earth snake. They originally cooperated to get food and survive, but eventually evolved to eat the other as food. One of them evolved into the Dark Ones, and the other evolved into the Encyclopods (it is currently unknown which progenitor evolved into which current-day species, the shapes of the Dark Ones and Encyclopods may suggest that they came from the snakes and frogs, respectively). The Dark Ones preyed on all life, making many species extinct, while the Encyclopods defended all life, and fought with the Dark Ones. Eventually, the life giving Chi receded, which killed most of the Dark Ones, and Encyclopods.

The war ended when the last Dark One (Leo Wong exterminated all the others) was killed by the last Encyclopod, which was hatched from the Violet Dwarf Star.