When the Graff went off to fight the Alliance Wars with the Cyrrhenic Empire, he was deposed by his people who hated and feared him and replaced by his half-brother. He swore vengeance. The Graff offered to buy Ribos from Garron, hoping to turn the planet into a training ground for an army so he could retake his throne. He also viewed it as a possible means of rebuilding his fortune by mining the jethrik that he believed was to be found there. Throughout this time, he was served by his long-time aide Sholakh.
When the Graff found out that he had been conned, he tried to kill Garron and the Fourth Doctor, who was working with Garron to recover the jethrik. Graff and his men pursued the Doctor and Garron into the catacombs, where Sholakh was killed in a cave in. This saddened the Graff greatly, and he promised to avenge Sholakh's death by annihilating the planet's people.
The Graff had his last soldier fitted with an explosive device so that he could "start afresh". However, the soldier was in fact the Doctor, who covertly placed the device on the Graff by sleight of hand. Unaware that he was now carrying the explosive, the Graff wandered off through the caverns in madness, calling on Sholakh to lead his troops on the attack. He was killed when the device detonated. (TV: The Ribos Operation)
Graff Vynda-K was a tyrant and psychopath who enjoyed killing people. After being banished by his own people, he swore vengeance and wished to take back his throne from his half brother. He was also very greedy and obsessed with being rich and powerful, never being satisfied with the power he already had. Despite his psychotic and ruthless personality, the Graff was genuinely devastated when his loyal second-in-command Sholakh died. Once again he swore revenge but this time out of remorse. The loss of Sholakh caused him to go mad and he deluded himself into thinking Sholakh was still alive, ordering him to lead his troops into battle, shortly before being blown up. (TV: The Ribos Operation)