This power source appears to be a fist-sized block of circuitry and is considered to be one of the "Hearts" of a TARDIS
(like a Time Lord a TARDIS has two).
It is located inside the console in the Control Room. The other Heart is Copy Eye of Harmony, which
is located deep beneath the console - at the other end of the Time Sceptre.
Orbital
Energy
from the Dynamorphic Generators
is stored in the
Main Space Time Element
(aka the Heart). The Heart of
the TARDIS also contains Huon particles.
The Time Lords invented Huon Energy for their time travel technology.
Huon Particles need something living (like a TARDIS) to catalyze inside.
Catalyzed Huon Particles magnetize to other Huon Particles
drawing them across Time and Space.
They also turn energetic muons into counter-magnetization thrust.
When inert Huon Particles are safe, but if given a chance to catalyze in a sentient being they become deadly. Billions of years ago the Time Lords wiped out virtually all Huon Particles (outside of TARDISes)
and Fluon Radiation
in the cosmos by unravelling their atomic structure.
It is possible that Huon Particles generate Fluon Radiation which can amplify and purify Artron Energy.
Using the magnetism of Huon Particles
the Orbital Energy
(energetic muons)
created by the Dynamorphic Generators is accelerated into counter magnetization thrust.
This energy is released through
the Heart's space-time portal into the Vortex
to push the TARDIS through the 5th Dimension. This makes
the Space-Time Element is an essential component for Vortex travel.
The energy in the TARDIS's Heart is the soul of the TARDIS.
If one gazes into the heart
(without first deactivating the safety systems)
one sees not only the Heart of the TARDIS, but also the Space-Time Vortex.
The TARDIS will be able to directly understand the viewer's thoughts and emotions by converting them into the language of Time itself. It is the only way for a being to have complete rapport with a TARDIS.
The energy of the Vortex would give the viewer power
over Time and Space.
They would be able to use the Power
of Creation
to alter all of History with a thought. This has been referred to as the Bad Wolf Scenario. If a Time Lord absorbed the power they would become a vengeful god.
If the viewer was not equipped with symbiotic nuclei
they would become one with the Vortex -
a dimension
of pure thought with a complexity that
borders on
sentience. They would be under the direct control of the Vortex.
Unfortunately it is also incredibly dangerous to look into the Heart.
Every time the TARDIS 'speaks' to the viewer it runs the risk of altering the subject's biodata,
possibly reversing the aging of a viewer, turning an adult into an infant. The viewer will also be exposed to all the
artron
energy flowing through the Heart and into the Vortex - irradiating them with a lethal amount of energy. A Time Lord can funnel most of this radiation back into the TARDIS and burn up the rest with a regeneration. However a member of a lesser species would find themselves slowly dying.
The Recall Circuit is part of the Main Space-Time Element. Remote operation of a TARDIS drastically reduces the life span of its Space-Time Element. This problem can only be solved with a Stattenheim Remote Teleport Control. A replacement Element must be coded to match the specific Type of the TARDIS's Time Rotor. When a TARDIS has materialized, the Element is easily removed, but removal in flight requires deactivating several safety systems in the corridor outside the Secondary Control Room. If the Space Time Element is removed in flight the Time Column will jam (possibly causing the TARDIS to leave the Time Spiral) and the internal dimensions will start to destabilize. If this should happen the operator should immediately activate the safety cut-out or a TARDIS will begin to break up from dimensional instability. If a breach were to occur in the force fields surrounding the Heart (say if the Time Column came all the way out of the console), the released energy would be enough to blast an unprotected person to atoms in seconds.
A TARDIS can "catch" anyone who dies by entangling their time stream within time fields created by the Heart of the TARDIS. This allows a TARDIS to bring those who die back to life by fixing the victim (biologically speaking) at a specific point in time
before they died.
There are several ways this can happen. The most likely situation occurs when a TARDIS is accidently positioned obliquely between two irrational time interfaces.
It can also occur if the TARDIS systems are preset properly
(though this would constitute a violation of the Laws of Time). A third possibility requires someone to gaze into the Vortex in the Heart of the TARDIS (aka the Space-Time Element) gaining power over Space and Time.
People resurrected using the power from the Heart of the TARDIS are effectively immortal. If killed by, say a bullet to the brain, they will quickly recover. They can never stay dead because their physical being is anchored into history itself. They might also be able to heal others. Because they are fixed in time they are seen as an obscene violation of the Laws of Time such that it takes a significant effort of will for either a TARDIS or a Time Lord to knowingly interact with such a person.