Zilgor

Zilgors were an advanced telepathic race. Six of them came to Bruhl, where they taught the native Glacians how to develop their civilisation and gave them their knowledge. Many years later, the Glacian Rraprro tried to kill them by freezing them in a block of ice, but they survived by placing themselves in a trance. They left a thought-cube for the Glacians telling them what had happened, which the First Doctor accessed for them. Presumably, the Glacian rebels succeeded in rescuing the Zilgors. (PROSE: Justice of the Glacians)