Mega-Shadow

The Mega-Shadow is a Pureblood Heartless that is found in Kingdom Hearts 358/2 Days.

Design
A Mega-Shadow has a vaguely humanoid body structure. It has a round, spherical head with circular, glowing yellow eyes. It also has two long, twisted antennae sprouting out of the top of its head. Each of its hands has three clawed fingers, and its feet are large and lack any discernible digits. With the exception of its eyes, this Heartless's body is completely pitch-black. The Mega-Shadow is identical to the basic Shadow and Gigas Shadow, and is between the two in size.

The Mega-Shadow’s name references its large size—"mega-" is a prefix meaning "large" or "great"—and its otherwise identical to basic Shadows.

Strategy
At the start of the battle, Lock-On to the Mega-Shadow. Ignore its smaller brethren, as Xaldin will handle them while you attack the Heartless. The Heartless will sink into the floor, rendering attacks useless. Once it resurfaces, start hammering the beast with the Keyblade. Use caution, as the Mega-Shadow may attempt to knock the player back with a slash attack. This is this Heartless Boss's only tactic.

All in all, this Boss Battle should be fairly simple, so long as the player utilizes Magic and doesn't keep too close. Use the Limit Break to finish the battle. Keep this strategy in mind for any further encounters with the Mega-Shadow in Beast's Castle or Twilight Town.

Trivia

 * In the first encounter with the Mega-Shadow, the battle music is "Tension Rising". In other appearances in Twilight Town, the battle theme is the normal "Sinister Sundowns".