The Megacosm is an Axe Sword that can be wielded by Lexaeus in Kingdom Hearts 358/2 Days. It can be upgraded to Megacosm+ and Megacosm++.
The Megacosm’s handle is a short, black rod with a short, orange spike in its pommel. Its counterweight is a wide, brown, arrowhead-shape. It has an enormous, curved, zig-zagging blade with smooth edges. The majority of the blade is orange, while its edges are silver.
"Megacosm" is an archaic term for the word "macrocosm"—a single structure that contains many smaller ones, such as the universe. The trinity of "Heaven, Earth, and Man" is an important tenet of Confucianism, and appears in many places in Chinese and Japanese philosophy. They are considered the most important aspects of a battle, and Japanese Ikebana arranges flowers in a triangular pattern to symbolize these three tenets as well.
The Megacosm's ground combo starts with Lexaeus performing a forwards run, holding the weapon sideways in front of him, followed by a quick ramming attack, and ends with a one-handed 360° slash. The attacks Lexaeus performs while wielding the Megacosm+ are identical to the ones he performs with the Megacosm. The attacks he performs with the Megacosm++ are nearly the same, although his charge on the ground is much longer.
The aerial combo consists of a single one-handed sideways slash.
 See also