Load up Firefight any map, They come about the 5th wave, maybe 5 min's in, they usually are accompanied by Fuel Rod Chieftains, I'd attempt normal 1st if ur alone. They are quite Regal 2 look at. Also U can do the Campaign Mission when U fight all the Banshees & Phantoms from the outside deck, u cross a big beam 2 get there, it's right after Alpha Site & Elevator, U fight one & there's a great cinematic showing 1 swinging his Hammer about @ ur Team. Lastly , becareful what U wish FOR.
Found it: cut & paste: http://www.youtube.com/watch?v=SGdhtDIVJzY
[Edited on 07.04.2011 12:12 PM PDT]