Basement Level 3 has less space than Basement 1 or 2. Each basement is reduced in size in comparison to the one above it.

When Garik first visits Basement 3, it has a "squashed" feel to him, as though the Tower is pressing down on it and compressing the walls. The ceilings are lower, the hallways narrower, the living quarters smaller. Even the finishes on the walls are of less quality than on the two floors above.

Basement 3 contains living space for the failed hybrids, many of which are perfectly functional but not able to mingle among normal people without attracting attention. Basement 3 has separate kitchen and dining facilities for its occupants.

On this level are also the soundproof training facilities. These facilities comprise the bulk of the space on Basement Level 3.

We first visit Basement Level 3 in Book 2 of The Human-Hybrid Project, Inside the Darkness.