There are two known types of spheres - spontaneous and created.

Spontaneous spheres represent the most stable spheres.  They cannot be restricted, and their settings cannot be changed.

The Heartlands is an example of a spontaneous sphere.  It has no known or proven creator, and has never responded to anyone trying to control it.

• It can be traveled to by any method - walking, flying, a spaceship, a wooden ship, a draphibian, a magical gate - any method of transit you can think of will let you enter the Heartlands.
• All levels of technology function within it - from medieval looms to advanced spaceships.  All levels of technology can enter it.
• All levels of medical care are possible - prosthetics, medical care for organics that can allow the regrowth and attachment of new limbs, artificial prosthetics, typical treatment of illnesses, artificial wombs, etc.
• The Heartlands has a regular seasonal cycle, similar to Earth - summer, autumn, winter, and spring.
• There is a day-night cycle, with a moon and a sun.
• Decay is possible - if a piece of meat is left out, it will grow rotten.

Thornveil Keep is an example of a created sphere, known to be controlled by a lockette named Cassandra.

• It can only be traveled to by walking or in a cart drawn by animal.
• Technology within the Keep seems to be predominantly paused at the level humans would refer to as ‘early Victorian’.
• Most medical technology within the Keep does not work, unless it is being used by Cassandra herself.
• Thornveil Keep only has the seasons of autumn and winter, and cycles unpredictably between them.  It displays particularly harsh weather when someone is within the sphere, to push them to seek shelter in the castle.  Torrential rains, near-blizzard conditions, and dangerous thunderstorms have all been observed.
• It is always nighttime in Thornveil Keep.
• Decay works much faster in Thornveil Keep than in the Heartlands, and wounds will become dangerous far more swiftly.

As you can see, there is a great deal of difference between these two spheres.  The listed criteria (travel, technology, medicine, seasons, day/night cycle, and decay) are the only settings a creator seems to be able to effect.  (It is presently unknown what causes some spheres to possess different gravity than nearby spheres, but it does not seem to be a setting a creator can control).

You may wonder at technology and medicine not being connected, as do researchers.  The best hypothesis is that it is because ‘medicine’ is primarily for organic species, it is separated from technology, which can impact and be utilized by most species.

All this, of course, leads to the next question…