The Antithesis, plant-based monsters that will devour everyone in their way, have been plaguing the galaxy for thousands of years. Twenty-five years ago they reached Earth. The Protectors are an interstellar alliance that opposes the Antithesis. When the Antithesis attack her graduation party, Caitlin MacCallan is chosen by the Protectors to fight them. She will find more than just Antithesis to fight...   This is a crossover fanfic of Ravens Dagger's Stray Cat Strut and Aest Belequa's Halcyon Nightmares (old version). Aest Belequa has started rewriting Halcyon Nightmares some time ago. The new version is titled The Halcyon System and different enough that rewriting this story to match the new world building does not make sense. I'd rather complete it based on the old lore (not anytime soon!) and then try my hand at an original.