The Tigellans are a race of near-humans native to Tigella.
Tigellan society is split between two groups: the Deons and the Savants. The Savants are the logical scientists of the Tigellans who run the planet and want to study the Dodecahedron. The Deons are the religious Tigellans who worship Ti and believe the Dodecahedron to be a holy object.
The Tigellans live underneath the surface of Tigella due to the dangerous plant life on the planet. Meglos, a Zolfa-Thuran, disguised himself as the Fourth Doctor and stole the Dodecahedron. Lexa, leader of the Deons, did not believe the real Doctor's tale of someone using his appearance. The Deons staged a revolution in anger at the Doctor's admission into the power room. A Gaztak party attacked the Tigellan city and took the Meglos and the Dodecahedron back to Zolfa-Thura.