Awoken by irregularities in the Earth’s atmosphere and plate movement, Arstron was the first monster that Ultraman Jack fought after fusing with Hideki Go.

It specializes in attacks that utilize its tough body and the horn on its head, and it can also fire a Magma Ray from its mouth.
After appearing near Asagiri Volcano, it ravaged the village situated at the bottom of the mountain. Undeterred by airborne attacks from the MAT Arrow 1 and MAT Gyro it continued its rampage, surrounding the village in flames with its Magma Ray.
Go drove from Tokyo to Arstron’s location, then transformed into Ultraman Jack and rushed into battle. Arstron attacked using its robust tail and horn, but after its horn was broken off by a karate chop, it took a Spacium Beam to the head and perished.