Saritan

A race of humans who first interacted with the Tollan when they had reached the equivalent to Earth technological development. Whether they were in need of a source of power, or their neighbors were eager to trade, the Tollans gave them a device to create unlimited energy. Instead, the people of Serita used it to manufacture war.

In only one revolution of planet Tollan, Serita and all her people were annihilated. The shockwave shifted the orbital track of Tollan, causing massive seismic disturbances. Eventually the Tollans had no choice but to flee in their ships.

This dark time for the Tollan have taught them to be cautius of outsiders, and to waive the option sharing their technology, no matter how benign a race's intentions are.