Though they were once noble, faithful servants of the Light, the High Council fell under Mephisto's sway after he was imprisoned within the Temple of Light in Travincal. Now they are devoted servants of the Lord of Hatred, supplying him with information and carrying out his orders by turning their misguided followers into hate-driven fanatics.
The High Council has been turned into Council Member demons, and players are ordered to kill the High Council in order to free the country from Zakarum's grasp. When the High Council has been destroyed, Zakarum Zealots will no longer attack but instead flee when a player approaches.
There are also several unnamed minion Council Members. In Lord of Destruction, players encouter another pack of Council Members led by Bartuc The Bloody when battling Baal's minions. It is unclear whether these Council Members belong(ed) to the High Council as well.