"First, he pointed that giant metal rod at me and out came a glass vial, it exploded next to me! Next thing you know, out comes a friggin’ bear! Then, as if that wasn’t bad enough, he sticks it in the ground. It expands and he walks into it to get a snack!" - Xzud, Experimental Arms Dealer.
Most large mammals, such as elephants, rhinos, and their modern ilk are ill-suited for domestication, but that doesnt exclude their use as engines of war. Rather than raise and train the Mammoth from birth, Mammoth Handlers instead capture the wild Mammoths at a young to juvenile age and train them for war. These animals are draped in armor and are unleashed as living war machines against the foes of the Mammoth Tribe.