Thanks to your help, I have managed to kill that lizzord!
May be it would be more harmless for Gael Serran population to leave him there as a stone monument? Of course, if he can be ressurected he probably can be unstoned as well. But still there always is a chance to return to Valeia at the end of the game (and after killing Grue near Brimloch Roon) and to check whether his stone copy be there. Also, what do you think of the fate of Garreth if Grue is stoned?
Thank all of you for the help once again!
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Sincerely Yours,
Tanda