In his conquest for world domination, Nene formed Gran Kingdom and orchestrated various attacks like the Land Shark at Talta Village, the Devee sickness at Lago Village, a blizzard at Noluta Village, and manipulating the robots of Baroy Town. He and his army of Mecha Robos ran afoul of Shu, Kluke, Jiro, Marumaro, and Zola. Gran Kingdom was defeated when Nene was destroyed.
In the anime, Gran Kingdom was enhanced with soldiers in artificial shadow generating exoskeleton armor and shadow wielders who allied with Nene. Their main base of operations is Nene's Flying Fortress; Galleon which is used to uproot locations like Jibral and Raqueeva.
When it came to the Hippopotamus Ruins, Nene plotted to drop it upon Coreed (where Conrad L. Lawrence was meeting with some Knight Masters). This was thwarted when Blue Dragon redirected the falling ruins from Coreed. While Shu's group fought Nene, Conrad and the Knight Masters fought the Black Shadow army. The Galleon crashed to the ground after Nene's defeat.
Due to Nene's destruction, Gran Kingdom was dissolved, most of Gran Kingdom's forces were reported to either fled or even deserting. Some even joined up with General Logi when his group succeded from Gran Kingdom to form Rosekstan.