In Origins, there are three Rieses that roam the map, and they are described as "thousand-foot-tall robot abominations." Their names are Freya, Odin and Thor, named after three gods in the Norse mythology. In The Giant, an unfinished Riese is present in the background of the map.

Which staff goes in which robot?

The Wind staff needs to be planted in the head of the robot named Odin, which is the one in the middle, and the Ice staff needs to be in the head of Freya, which is the robot to the left. Once you've planted these staffs, go to the excavation site and place the fire staff in the new pedestal that appeared here.

Why are there giant robots in origins?

The Robots were created by Group 935 to help the Central Powers win the Great War. Two main scientists, Ludvig Maxis and Edward Richtofen contributed to their construction. According to Richtofen, building the Giant Robots was only possible due to Element 115.