Hologram of a notorious Cardassian exobiologist whose medical knowledge, built on Bajoran suffering, the Doctor needed to save B'Elanna Torres.
Crell Moset was a renowned Cardassian exobiologist. In Nothing Human, the Doctor created a holographic version of him to help remove an alien lifeform that had attached itself to B'Elanna Torres. Played by David Clennon, the hologram was brilliant and collegial.
The crew learned that the real Moset had built his expertise through lethal experiments on Bajorans during the occupation. Torres refused treatment from him, and the Bajoran crew protested. The operation succeeded, but the Doctor then deleted the Moset program, deciding that its knowledge came at a price he would not pay.