Amalgamate is one of Senshin's original jutsu. First, he performs the hand signs. Next, all the area around him appears to fold up, being replaced by flat grassy land. From the center of that area, Senshin reappears as a gigantic being, covered in everything that was previously there. In a desert, he would appear as a sandy being with cacti on him, in the mountains as a rocky being, etc. This greatly increases his abilities.