The Trinni/ek were a humanoid race from the Alpha or Beta Quadrants. They were hairless, with brown to black skin, and moved about on their long arms along with their legs, much like some Terran primates.
The Trinni/ek's native world had become uninhabitable thousands of years prior to the 24th century, possibly due to a supernova. The survivors (referred to in later legends as "the landers") emigrated to a new planet, also dubbed Trinni/ek. That planet's sun generated a particular magnetic field which overstimulated the peripheral nervous system of most carbon-based life forms. Though this caused great physical hardship in the early years, the Trinni/ek were able to adapt to this field over generations, and eventually became physically dependent upon it.
In late 2379 or early 2380, the Federation Starfleet starship USS Io made contact with the Trinni/ek. The Trinni/ek, led by Speaker Ytri/ol, were eager to forge diplomatic relations with the Federation, and worked for several months with Federation Diplomatic Corps Ambassador Colton Morrow, leading up to a state visit to Earth. However, Ytri/ol and his party began to suffer ill effects after leaving their system, culminating in a paranoid outburst in the middle of a formal dinner hosted by Federation President Nanietta Bacco and other Federation government officials.
Ytri/ol returned to Trinni/ek fearing he had provoked a war with his unexplained behavior, and apologized to Captain T'Vrea when the Io made a return visit shortly thereafter. Unfortunately, a second visit to Earth, to address the Federation Council, resulted in more illness, with the Trinni/ek delegation collapsing in the middle of the Federation Council Chambers. Following this, Second Speaker Rale/ar accused the Federation of kidnapping their leader. Fortunately, Chirurgeon Ghee P'Trell, the head of Starfleet Medical, was able to determine the cause as being the Trinni/ek's dependence on their sun's magnetic field. The delegation recovered upon returning home.
Two months later, the Federation reached an agreement with the Strata, a silicon-based species (and thus unaffected by the Trinni/ek sun's magnetic fields), to act as intermediaries in continuing negotiations with the Trinni/ek. (ST novel: Articles of the Federation)