Unknown (allied with
Shadows and Drakh)
Shadow Surgeons were an unidentified humanoid race that once served the Shadows.
Serving their masters as medical technicians, they are known to have prepared sentient beings with
cyberweb implants and installing them as living CPU's in Shadow Vessels, as well as examined potential hosts for Drakh Keepers.  
Following the departure of the Shadows after the
, this species remained allied with the Drakh, another race that were allied with the Shadows. They followed them to
and hid inside the many forgotten secret passages within and beneath the
Centauri Royal Palace
 Londo being experimented on the the Shadow Servants.
A Drakh and Shadow Servant, observing Londo.
The name "Shadow Surgeons" is purely a descriptor as no official name for this race has ever been given in a canon source.
This species looks similar to, but is distinct from, both the Streib (another Shadow servant race) and the Vree (members of the League of Non-Aligned Worlds/ Interstellar Alliance).
Mongoose Publishing sourcebook "Darkness and Light" names this race as the 'Zener' and states that they posses an instinctive grasp of Shadow Technology, thus serving strictly as scientists.