Archetypes are basic categories all objects and beings within Nested fall into, and are exactly what they sound like.
Ancient: An old world, inhabited with dinosaurs and other animals, as well as tribal peoples.
Terraformed: A modern-day world, with modern technology and culture.
Medieval: A medieval styled world, inhabited by various magical kingdoms. Additionally, all medieval worlds contain several "dungeons", vast areas with magical creatures (all of which are terribly bloodthirsty) and items.
Future: An advanced world, with nanite technology. Nanites are an integral part of their culture, and have done such things as allowing humans to live for centuries and replace limbs.
Dyson Sphere: See link for details.
Small, Large Creature Archetype: Describes a medium-to-small creature, like a bear, or a gnat.
Humanoid Creature Archetype: Describes humanoid beings, most often magical ones, however their thoughts reveal at best, indifference towards humans, and at worst, manic bloodthirst.
Sea Creature Archetype: One of the most interesting archetypes, these beings are found in dungeons, and are similar to Space Monsters, immortal, eldritch beings, only earth-bound. Their thoughts are in all caps, and usually exposit on the creatures' madness or anger.