The Tandu are a fictional extraterrestrial species from David Brin's Uplift Universe. Physically they are a spindly insectoid species. They are capable of regenerating severed limbs and even heads. If forced to humiliate itself by conversing with a member of an alien species as an equal, a Tandu will cut off one or two of its own legs as a form of ritual purification. A Tandu who has been deemed by his superiors to have failed unforgivably is expected to commit suicide by cutting off his own head (the body survives and eventually grows back a new head, but presumably the original personality dies with the brain).
Like many Uplift Universe species, the Tandu worship the Progenitors (a semi-mythical race that lived one billion years ago and created (uplifted) the first intelligent species) and would by our standards be considered religious zealots. They are a highly xenophobic species, viewing all other intelligent lifeforms simply as enemies or tools for them to use. They follow the "Inheritor" sect of the cult of the Progenitors, believing that upon the return of the Progenitors (an event roughly equivalent to the Christian Rapture in many Galactic mythologies) the current power structure of galactic civilization will be destroyed and the universe will be cleansed of "unworthy" races. The Tandu believe they will be given the privilege of being made the Progenitors' holy warriors, who will slaughter the unworthy upon their return.
The Tandu have created at least two slave races that are powerful psychic adepts: Episiarchs and Acceptors. The Tandu may have violated the rules of the uplift institute by making them truly dependent on them. The Tandu have had records of their clients sealed.
Incrementors were the Tandu's first Client race, their being listed last in formal introductions likely indicates a demotion in status. They resemble multi-legged dandelions with sensory nodules circling below a globe of soft fuzz. The are likely Psi-adepts like the rest of the Tandu client races. How they serve the Tandu is unknown.
In the same novel, a Tandu warship used a probability engine, directed by an Episiarch, to leap into the middle of an enemy formation. The ship created a great deal of destruction, before the Tandu ship ceased to have ever existed. The risks of this probability drive deter most non Tandu races from using such technology.
The Tandu have fought several minor skirmishes with the Earth Confederation. They are described as being extremely dangerous enemies, often winning even when the numerical odds favored the humans. This may not necessarily say all that much about their prowess, as humans in this universe are an extremely weak race (they can perhaps be thought of as being in a similar position as rogue states like Cuba and North Korea in our world), but more advanced alien species seem to respect their abilities. The Tandu are organized as a raiding force and use mostly Battlecruiser-like ships with great speed and firepower but poor protection that rely mostly on not getting hit for their survival. A Tandu light destroyer was described as being equipped with "antimatter beams", possibly antiparticle beams or possibly more exotic antimatter/matter conversion weapons similar to Minbari antimatter cannons (the latter seems more probable as the destroyer fired them in atmosphere - an antiparticle beam fired in atmosphere would react explosively with the air and probably do more harm to the firing ship than the target ship).