The Ogri are a species of silicon-based creatures, first shown in The Stones of Blood.
Ogri are large creatures native to Ogros. They look like large, glowing rocks, usually taller then a human. They are large and heavy, sometimes weighing as much as 3.5 tons, but they can take a lot of damage. Like other silicon-based lifeforms, they break down into grit when killed. They feed on proteins, which are common on Ogros. When on Earth, the Ogri had to rely on the globulin in blood, which they could absorb by touch. Ogri were not shown to communicate and did not show any signs of intelligence.
Cessair of Diplos took 3 Ogri from Ogros, which she used for protection and to impress the humans of Earth.