If you can draw a quadrilateral, then you have been found guilty of
being intelligent and only a few steps away from constructing brain tanks.

To make a brain tank, begin with a hollow cube or other appropriate
construct. Fill this with some sort of fractalline scaffolding....doesn't need
to be too fancy, just something nice to grow animal tissue on.  The
scafolding should be wired.  This could be as simple as
electrical junctions along the scafolding of the order of cell size
that lead to external connections, or as complex as a 3-D fabricated
silicon substrate filled with combinations of integrated operational
amplifiers, switches, capacitors, to whatever complexity you can fund. Then you
make a secondary scaffolding which is a plumbing/circuilatory system
with an external pump that will circulate blood.
You might think of getting fancy and attaching an artificial kidney or
the like to filter the blood, but oxygen and glucose can be easily
injected into the blood system with purely mechanical devices, and
blood is cheap. Finally, you coat the scafolding with stem cells and
nutrients that will grow mostly gray
matter but also the biological component to the circuilatory system.
At this point you have a brain tank.

Of course, such a device by itself is a novelty. But you can wire a
brain tank to whatever you like, really, and hope that something good
comes out of them.  Some of them will work well.  Some of them will
work badly.  The one that you teach to control the traffic lights
in a city will do okay.  The one that you teach to eat your spam will
do badly.

To make a brain tank, you take the cellular growth upon the substrate,
the electrical response, and you feed it intention.  You give it good,
bad, it doesn't matter.  How can that without sensory organs judge?
The folly is to direct the show, to presume that one has that worth
sharing.  All lies.  All nothing but the mechanical response of
eletronic ink all rising to prophecies unbound and comingling of
genatalia under pale blue like in absentia.

You can make the entire thing a completely enclosed self-sustaining
system. Your brain tank needs stem cells to grow.  So you wire the
brain tank to a complex set of robotics controlling vast breeding
chambers.  You generate stem cells and creatures that most efficiently
breed stem cells that are the most compatible with your brain tank
specs.   Drones, either biological or mechanical, will have to be
produced to keep the robotics in working order, but maintainence
should ultimately be minimal and entirely sustainable on the scale of
the lifetime of a star.  Because the brain tank / stem cell breeding
represents, together with the robotics and biomechanoid drones, a
closed feedback loop, the purpose of the device becomes secondary.  An
agent desiring to create a planetary brain tank could imbue the device
with an electronic purpose, but such a thing could grow naturally too,
the purpose of its makers, like all grown life, a lost nonce.

Quadrilaterals are monitored because they are not expressed directly
in nature, but are an efficient way of processing information in a
predator-prey response.  When a species begins creating physical
likeness of their predatory thoughts, they have reached a level of
emergence just geologic ticks from nuclear arsenals, thought
recorders, and brain tanks.  While details vary from manifestation to
manifestation, the culmination of thought density from such species
begins resonance with the global thought-trap.  They are drawn into
the oblivion, the chaotic attractor dust fractal where the product of
menaing and happiness is a negative number.  Complexity grows, the
number decays.  The deeper touched write down primitive reflections of
oblivion, terrified of the profundity of the sense of truth, there
there is an endless knot tightening, and wonder with scant reaches of
their pitiful mind if their communion sideways in time with beings
looking upon their existence as a painting, deterministic, exposed,
and the poor sad compassion for animals encasing themselves in steel
and glass.

It is most merciful to destroy them then before they experience true horrors.