Thijarian remnant

The Thijarian Remnant was a collection of DNA fragments from many dead the Thijarians had "witnessed". The remnant contained carbon, phosphorous, oxygen, nitrogen, sulphur and calcium. The Thirteenth Doctor stated that it was the densest organic material she had ever seen. After observing the death of an individual, they would collect the individual's DNA in a cloud of purple dust.

The Thirteenth Doctor, Ryan Sinclair, and Prem saw Kisar and Almak standing over the body of Bhakti. After the Thijarians had transmated away, they also saw the dust rise from Bhakti's body. (TV: Demons of the Punjab)