Portals are found often,
throughout many different Worlds.
As a generalisation;
a Portal is a Standing Stone (Menhir),
a Stone Circle, a Dolmen (Shelter),
or other similar arrangement of monolithic stones
where the stones contain a significant quantity of quartz
(and other minerals)
enabling a raw, natural, bioelectrical, geomagnetic flux
to channel through them.
Their rules for use do vary from world to world.
For example;
in some worlds you can travel
from a circle to a circle or a stone,
but not from a stone.
Many so-called experts agree that their uses
are more in the realm of mystery
than the realm of the known,
therefore it is always possible
someone may happen along who knows
how to activate a different quality from the Portals
than any known about by the locals at this time.
They are ancient.
There are vastly more in existence
which we do not know about,
than the number we do know about.
The organisation which knows
the most of all about them
are the Druids,
who are often half-mad
and always very secretive.
The Druids warn;
using the stones can be dangerous.