Well, i imagine it wasnt an actor. it looked like one of those cheesey talking christmas trees that you see in the malls with some dude inside pulling ropes and levers. Dont know if everywhere has those in the malls around them but make pizza the hut green and you get the legists.
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and filled with wrath and despair he mounted upon Rochallor his great horse and rode forth alone, and none might restrain him. He passed over Dor-nu-Fauglith like a wind amid the dust, and all that beheld his onset fled in amaze, thinking that Oromë himself was come: for a great madness of rage was upon him, so that his eyes shone like the eyes of the Valar.