Cheers mate! The arms are fairly ordinary parts from the Termie Lord kit. The left one is the one holding the staff. I just cut it at the wrist to turn the hand a bit and replaced the top of the staff with a hammer from the Ogre Kingdoms Ironguts.
The right arm is the arm that holds the Bolter from the same kit. I cut off the hand and replaced it with a huge claw from the Dark Eldar Talos/Chronos kit.
Hope this helps!