Drago Pettrovich Madnar is a brilliant scientist that first appeared in the original Metal Gear as a hostage of Big Boss and the forces of Outer Heaven. He is forced to develop the Metal Gear TX-55 under threat of harm to his captive daughter, Ellen. He assists Solid Snake by providing him with the information necessary to destroy the TX-55, and he and his daughter both are successfully rescued.
In the years following the events in Outer Heaven, however, Dr. Madnar has a falling out with the greater scientific community, and begins to feel that Big Boss may have been right all along. He voluntarily travels to Zanzibarland and begins work on the Metal Gear D, an improved model of his original TX-55, though the outside world is led to believe he has been kidnapped once again along with his friend Kio Marv, the Czech scientist responsible for the discovery of OILIX.
When Solid Snake infiltrates the Zanzibarland compound where he's supposedly being held captive, Madnar pretends to be held hostage and provides some level of assistance. However, Madnar kills Marv when he refuses to divulge the process of OILIX creation. He ultimately attacks Snake as well, but is defeated.
Following his defeat, Madnar goes into hiding in eastern Europe, where his research leads to the discovery of white blood for cybernetic organisms. He manages to help Raiden twice; first after Raiden is made into a cyborg, and the second time after he is gravely injured by Vamp in Metal Gear Solid 4.