Neoshadow

The Neoshadow is a Pureblood Heartless introduced in Kingdom Hearts Final Mix.

Kingdom Hearts Birth by Sleep
Back when Ventus was the apprentice of Master Xehanort, Xehanort called the boy to the Keyblade Graveyard and then summoned a swarm of Neoshadows for him to fight. Ventus was not strong enough to win with only his light, and although Xehanort ordered him to use the power of darkness to win, Ventus refused and was defeated. Xehanort instead decided to use his Keyblade to forcefully extract the darkness within Ventus's heart, creating Vanitas.

While Aqua is traversing the Realm of Darkness, she battles Neoshadow along with a few other Pureblood Heartless.

Kingdom Hearts 358/2 Days
After returning to the World That Never Was in order to reclaim Kingdom Hearts and revitalize Xion, Roxas is attacked by several Neoshadows. He eliminates them, but is forced to side with Riku in order to finish off the rest of the continuously spawning Heartless. As soon as the Heartless are taken care of, however, the two Keyblade wielders turn on each other.

Design
A Neoshadow has a more humanoid body structure than a normal Shadow, but shares the same pitch black skin and spherical, glowing yellow eyes. Its crooked antennae are quite long and fall back behind the Heartless. It seems to be rather muscular, and its hands are very large, each one sporting five clawed fingers. Its feet, like those of a normal Shadow, are long and lack digits, but a Neoshadow's feet more resemble boots. Its body is also lined by several faint, blue veins of color.

The name "Neoshadow" is derived from the prefix "neo-", which means "new", and "shadow".

Kingdom Hearts Final Mix
The Neoshadow is stronger and faster than a Shadow, and is more strategic in combat. The Neoshadows are among the most difficult common enemies, working together as a team to defeat Sora. Fighting Neoshadows is a multi-stage battle, and the stages change based on how many Neoshadows are alive. At the beginning of the fight, there are seven Neoshadows, who will attack by jumping into the air and spinning, then launching at Sora similar to the Bandit. They will also use basic melee strikes and sink into the floor to avoid attacks, similar to a Shadow. At this point in the fight, they can be affected by Stop magic.

After there are only four Neoshadows remaining, they change tactics and sink into shadowy portals that appear beneath them on the ground. Afterwards, nine of these portals will appear around Sora, and the Neoshadows will choose random portals to jump out of and attack simultaneously. After attacking, they land on the ground for a brief moment, then the portals reappear beneath them and they sink back into the ground. The only time they can be hurt at this stage is right when they land on the ground, before the portals appear beneath them once again. If a single blow connects with one of them, it opens a short window to execute a combo. At this point, Stop magic no longer affects them.

Once there are only two Neoshadows left, they change tactics once more. In this stage of the fight, a single Neoshadow will wander around the room, and has access to all the attacks and abilities of the earlier stages (instead of several portals appearing on the ground like stage two of the fight, the Neoshadow will just use it as a way to get close to Sora to attack him). It also retains the immunity to Stop magic. While this Neoshadow attacks Sora, the other one appears as a black portal beneath Sora, then partially emerges from it to grab Sora's leg, which prevents him from moving, attacking, or using magic for a brief period. To counter this, Sora can jump when the portal appears beneath him, but cannot hurt this Neoshadow in any way. Instead, Sora must focus on the other Neoshadow that moves around the room, and attempt to kill it instead.

When there is a single Neoshadow remaining, it will move to the center of the room and attempt to summon more Neoshadows. Six portals will appear on the ground in a circle around it, and new Neoshadows will appear within them, attempting to climb out of the portals back into the room. Instead of going after the last remaining Neoshadow, Sora must focus his attacks on the ones emerging from the portals, who will emerge as fully healed Neoshadows after several seconds. Once the emerging Neoshadows are slain, Sora can direct his attention to the final Neoshadow, and defeat it to end the fight. If Sora fails to defeat the new Neoshadows after a certain amount of time, they will emerge from the portals and the fight will reset to whichever stage corresponds to the new number of Neoshadows (7-5 for Stage 1, 4-3 for Stage 2, or 2 for Stage 3).

Other Games
In Kingdom Hearts: Chain of Memories, Kingdom Hearts 358/2 Days, and Kingdom Hearts II, they are less rare and dangerous but are still more difficult to defeat than regular Shadows. In Kingdom Hearts II, a powerful Reaction Command, Wind Dance, can be used to eliminate or intensely damage Neoshadows.