5 Invasion of Pern » by Kitsuneko A ship of parasitic aliens crash-lands on an unknown planet, and the survivors must plan an invasion. But this planet is in danger already, and it has protectors. There are dragons in Pern's skies, but while they fight against Thread's hazards, they are oblivious to a more insidious danger. That's left to five young humans and one alien to fight. No canon knowledge required.