When he learned he was dying in 2258, he arranged for his assets to be liquidated upon his death to fund an assassin from the Thenta Makur to kill his old enemy. He left specific instructions that a final message from himself was to be delivered to G'Kar (which informed G'Kar he would be dead within 48 hours). He wanted G'Kar to know fear and pain before dying at an appointed hour. The assassin he hired was Tu'Pari, but he was unable to carry out his order.
Du'Rog died believing his revenge was certain, never knowing it never came to pass.
Coincidentally, Du'Rog had previously sponsored a Counsellor Li'Dak to his position in the Fifth Circle, who in turn would later sponsor Na'Toth to her position as Ambassador G'Kar's diplomatic aide. This caused G'Kar no small amount of paranoia as she arrived on-board Babylon 5 at the same time as Du'Rog's final message was delivered.