The Thunder Golem is currently an untrainable/epic/exclusive troop, like Leviathans. This troop, while mediocre on offense, is a good defender (similar to the Frost Giant).
These troops have a 5x bonus on stats if you are defending, as I fixed at the top there are 2 pictures that prove they have an augmentation of statistics on defense. Sunsets with the entity troop stats brackets.
With the forge, if you put pieces that augment the attributes that have speed may suffer many casualties as they are the first to take damage.
This is a clear example that the Thunder Golems have augmentation of their statistics since stopped twice troops without casualties comments put an image that is 40 against 20 giving augmentation view attributes.