He had defeated the ogor tribes of Mawking Crackmarrow in order to claim the valley and set up his sronghold in the island at its centre, protected by the Sorrowmere and whose lingering life magic meant there was plenty to eat. There he raised idols to Gorkamorka, crudely fashioned from the ruins of the what had been Ghastenglor City. He was unaware of the Realmgate that lay beneath. 
The sylvaneth under Drycha Hamadreth drew him and his Ironjawz away whilst a wargrove of Clan Tethil truely awoke the isle and then unleashed it on the army of the Megaboss. Angry about being tricked, but unable to fight the waves of reawakened vegatation, he turned his Maw-krusha away to fight another day.