El Martillo

is a technique used by the Hollow, Ayon.

Description
Ayon's right arm rapidly enlarges to more than double its original thickness, bringing with it a proportionate increase in the arm's mass and, as a result, a drastic rise in its destructive power. When used against Captain-Commander Genryūsai Shigekuni Yamamoto, Ayon only resorted to the technique once enraged after being injured, but the subsequent attack failed to connect, due to Yamamoto's proficiency in Shunpo.