Aliens come to Alterra, in spaceships, or some sort of space travel.
Aliens manage to convince entire local population to fight for them, and probably 100s of thousands of these natives die every day from large animals that know magic and can wield weapons, yet still fight for aliens.
Aliens come to fight these animals, wielding the most technologically advanced stuff available, bows, swords, and occasionally fists.

Discuss.