The Heartless (ハートレス Hātoresu?) are beings of darkness that manifest in two forms, "Pureblood" and "Emblem". While most Heartless are, in fact, manifested hearts, they behave entirely devoid of emotion, and thus were named "Heartless".

Pureblood Heartless

Pureblood Heartless are natural Heartless, born from the darkness in people's hearts. They are ink-black in color, with yellow beady eyes. They are more common in places that are close to or saturated in darkness. Upon their destruction, they simply disappear in puffs of darkness, without a heart leaving its body. While Purebloods have less variety, they are far more numerous in quantity.

Shadow: A normal 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 black. Shadows emerge from the ground to attack with a simple but powerful scratch attack. These Heartless are easy to defeat on their own, but their habit of attacking in large swarms can be quite overwhelming. When facing swarms of Shadows, the Thunder spell is an effective means of finishing off these foes quickly. The Keyblade is sufficient enough to take down a Shadow when it is on its own, however.

Mega-Shadow: Mega-Shadows are larger variants of the Shadow, using similar attacks. They can sink into the ground to become invulnerable, but a well-timed magic attack may damage them before this occurs. While magic can be used to quickly eliminate a Mega-Shadow, physical attacks are recommended to eliminate them. They tend only to attack with a simple scratching tactic, which can be either avoided with Dodge Roll or protected against with Block. When a Mega-Shadow's attack is blocked with Block, it shall become stunned for several seconds and open to attacks. They may also perform a body slam; Dodge Roll a good way to avoid this. Mega-Shadows have little HP and can be easily eliminated, regardless of one's current skill level.

Gigas Shadow: A Gigas 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 distinguishable digits. With the exception of its eyes, this Heartless's body is completely pitch-black. The Gigas Shadow is identical to the basic Shadow and Mega-Shadow Heartless, but is much larger than either of its two relatives.

Darkball: The Darkball, true to its name, has a spherical body that is pitch black and streaked with dark blue. Its glowing, yellow eyes are rather small. The inside of its mouth is blue, and the mouth itself is a jagged, toothy opening. This Heartless has three thick, black and blue tentacles with frayed, pink tips sprouting out of its body; two are on its top, and one is on its underside. Darkballs are relatively easy Heartless to defeat; their attacks do little damage, they attack infrequently, and their HP is low. These Heartless teleport from one place to another in a way similar to the Invisible.

Bit Sniper: The Bit Sniper has a simple, but surprisingly frightening appearance. It has a large, black teardrop shaped body, black bat wings, which enable it to fly and crawl around, the classic Heartless jagged jawline, and bright yellow eyes; looking closely around the eyes, blue vein-like patterns also can be seen. The Heartless's name is a reference to its relatively small size, low strength and its ability to fire its lasers from long distances. A "bit" can mean a small amount of something, and sniper rifles are accurate weapons that can hit targets from considerable distances.

Possessor: The Possessor is a simple, gaseous creature that bears some resemblance to the Darkball Heartless, sporting a similar, jagged mouth—albeit the Possessor's is red—and glowing, yellow eyes. It is seemingly made up of black, dark blue, and purple shadows. The Possessor's name clearly refers to its ability to take control of inanimate objects. In this manner, it can become the Thresholder, as well as a Gargoyle Knight or Warrior. As long as a Possessor is touching someone, their health will be continuously depleted. Jumping or performing Dodge Roll will help escape its capture.

Gargoyle Knight: A Gargoyle Knight is a statue with a tall, rectangular pedestal colored in various shades of grey. It has four steel grey spikes in its base. The actual statue is the upper body of a thin, muscular gargoyle with steel blue skin and wings of the same color. Each of its hands has four clawed fingers, and it wears a grey armlet with silver spikes on its upper left arm. The gargoyle's head is roughly triangular in shape and sports large, angular horns that curve inward. Its face is black and it has small, yellow eyes. It also wields a grey sword with a diamond-shaped guard and a spiked pommel. The Gargoyle Knight's name refers to the creature the statue is modeled after. "Knight" may reference the fact that it carries a sword, as opposed to the Gargoyle Warrior.

Gargoyle Warrior: A Gargoyle Warrior is a statue with a tall, rectangular pedestal colored in various shades of dark grey. It has four steel grey spikes in its base. The statue itself is that of a muscular, wingless gargoyle with light grey skin and dark grey claws. The gargoyle wears heavy armor colored in shades of blue and grey. The armor also sports several tall, silver spikes. The gargoyle's face is dark grey, its eyes are yellow, and it wears a conical, steel blue helmet. It also wears steel blue gauntlets on each of its wrists. The Gargoyle Warrior carries a large, double-headed axe with a grey and silver blade, a steel blue handle with several pale yellow rings decorating it, and a silver spike on both ends of the handle. The Gargoyle Knight's name refers to the creature the statue is meant to resemble. "Warrior" may refer to its armored appearance and its use of a heavy axe as a weapon, contrasting with the Gargoyle Knight.

Invisible: The Invisibles are reminiscent of Darksides, possessing black skin, a similar muscular frame, and a heart-shaped hole in their torsos, but are smaller and more embellished. They have sharp purple and blue horns that form the outline of a curled heart.. They also have small blue bat-like wings on their back, gold-tipped feathered wings on their forearms, and bluish-purple fireballs under their feet, presumably assisting them in their fast movements and tying into their dark fire attack. Their long tails appear scaly, and end in a sharp, crescent-shaped blade. Unlike many Heartless, which tend to attack with natural weapons like claws or magic-based powers, the Invisible bears a scalloped, blue-bladed sword, which appears blunt, but can unleash powerful physical blows. The Heartless's name references its ability to disappear when using its "Ring of Fire" curse attack. The Invisible fires dark energy every now and then, and uses its sword to slash at their target. One of its special attacks includes throwing its sword in the ground, while the main body turns into a ring of dark fire surrounding their target. The ring of dark fire appears to circle the one closest to the Invisible. Once the time is up, the curse explodes, dealing large damage to any member of the party. Invisibles are a difficult type of Heartless to defeat due to their high hp and strength; they almost always appear in groups and thus can be a huge problem if the one fighting against them gets overwhelmed. Fights with Invisibles can be made easier through the use of Thunder, Gravity, and Aero magic.

Orcus: An Orcus is a muscular, humanoid creature with dark purple skin. The tips of its feet are red, and it has small, dark grey wings on its back. It also has an orange wing on each of its elbows. It has a long tail that ends in a silver, circular, pendulum-like blade. Its small eyes are glowing yellow, and its head features two large, conical, dark purple spikes on either side. It also has two horns with orange tips on its head that connect to each other to form a heart shape. It also carries an ornate, orange sword with a grey cross guard, black edges, and the kanji for "Hard Core" (硬核 Kou Kaku?) are written on the hilt of its blade. The Orcus is a rare and powerful breed of Pureblood Heartless that has a very similar fighting style to the smaller, less powerful Invisible. It is swift and will try to stay out of attack range, so the use of magic, particularly the homing Fire spell, is highly recommended. It is important not to use any Thunder spells, as they will heal the Orcus. A well-timed aerial combo is another good way to damage this type of Heartless.

Neoshadow: 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 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 opponents. Fighting Neoshadows is a multi-stage battle, and the stages change based on how many Neoshadows are alive.

Demon Tower: It is a mass of Shadows in a twister formation that attacks primarily throughout the Realm of Darkness, but appears in other realms when darkness collects in massive quantities. Its attacks are indicated by the Shadows' eyes glowing red: one in which the Tower rams its target, which can be defended by Barrier, and another in which the Tower divides into the Shadows. When the Tower is separated, the Shadows can be attacked and destroyed.

Darkside: A Darkside is a massive, muscular, humanoid Heartless with black skin. Its legs are rather short and its feet are very thin and curl upward. Its arms are quite long, and it has two relatively small, twisted wings on its back. There is a large, heart-shaped hole in the Heartless’s abdominal area, which penetrates straight through from the front to the back. Its head is covered in dozens of twisted, black tentacles. Only its small, glowing yellow eyes are visible. The Darkside battle shares many similarities with the Twilight Thorn, a gigantic Nobody...

Thresholder: The Thresholder is made up of two ornate statues carved into a grey, hexagonal doorway. Each statue has one arm "trapped" in the door, though their claws are seemingly grasping the gold lock in the center of the door from the other side. Each statue on the Thresholder takes the form of a muscular, black-skinned demon with a thin, jagged mouth, spherical head, and beady, glowing yellow eyes, similar to a typical Heartless. Its chest, exposed arm, and each of its short, pyramidal horns sport a jagged, yellow pattern decorating them. Each wears a green collar with four short, silver spikes on it, and their hands end in three red claws. Their backs are lined by short spikes, and their lower bodies are actually curled, interweaving tails with yellow tips. Their lower and upper bodies are divided by a thick, sky blue "belt". The Thresholder will attack by extending its arms across the room and summoning orbs of darkness, so try to avoid those. When its health depletes to a certain point, the Keyblade can be used to expel the Possessor from the door. The Possessor has no form of attack or defense, so simply attack it. Eventually it will float back to the door and reanimate it. Thresholder then begin shooting projectiles at the target. Move in close to attack without being hit. After its health is depleted again, Possessor comes out and floats around again. Eventually, Thresholder will extend its arms at full length, cross them over, and continuously slap its attackers. Both bosses must be defeated to end this battle.

Shadow Stalker: The Shadow Stalker's body is a black sphere with several twisted tentacles sprouting out of it. Two of these are large, each sporting two metal bands around them, while the rest are smaller and placed more haphazardly around the Heartless's body. The tips of all of these tentacles are orange. The Shadow Stalker's jagged maw is red on the inside, and its eyes are eerie, glowing, yellow circles with pitch-black rings around them. The most prominent feature of the Heartless are the two chains wrapped around its body, with each end of both chains attached to a conical weight. The Shadow Stalker is vaguely reminiscent of the Darkball Heartless. The Shadow Stalker shares the same ability as the Possessor Heartless: it can possess and animate any inanimate object. When in desperate need, it cocoons itself and transforms into the ferocious Dark Thorn.

Dark Thorn: The Dark Thorn is a massive creature with black skin. Its entire body is wrapped in teal thorns, possibly a reference to the Beast's rose, and both of its wrists and ankles still have manacles on them. The chains on its arms are broken, but the chain connecting its feet is not. Like many other Purebloods, the Dark Thorn has a heart-shaped hole in its chest. The Heartless has a large, red, toothy maw and beady, glowing yellow eyes. While it is muscular and has large hands and feet, it also has rather thin limbs. Each of its limbs sports three digits with long, red claws. The Dark Thorn also has two enormous, orange horns and a massive, orange mane. The battle with the Dark Thorn requires notably less strategy than the Shadow Stalker and is more of a straightforward assault. As the Dark Thorn, the Heartless is more agile and erratic, attacking enemies with its claws and sometimes using the chains to hit opponents. It can also summon Possessors to attack and can turn invisible to elude foes. The Dark Thorn is more agile when invisible and the fight becomes much easier when the invisibility is lost.

Demon Tide: The Demon Tide, much like the Demon Tower, is comprised of a swarm of Shadows. Unlike the Demon Tower, the Demon Tide is bigger, is wave-shaped (hence the name, "Demon Tide"), and has a core at the tip of the Heartless that glows either violet or orange. The Demon Tide has three attacks which are telegraphed by the Shadows' eyes glowing red. The first consists of it ramming a target, a manner reminiscent of the Demon Tower. It can also cough up Shadows, again like the Demon Tower, but they can and will trap enemies in a swarming combo if ignored. The third consists of it burrowing underground, its presence indicated by a cloud of dust. When the Demon Tide's health hits a certain point, it burrows underground, triggering the second phase of its battle tactic. The Shadows now surround the core in a twister formation. During this time, the Tide retains its ability to summon Shadows, but it also has a new attack in which its core rises upwards and fires globs of darkness that home in on targets. After some time, the Tide launches its targets into the air, firing the globs from underground. Gravity can pull enemies into its clutches.

Darkling: Born from Keyblade wielders who succumb to the darkness in their hearts, these Heartless retain the ability to speak and access the Lanes between, but unlike their human forms, they do not draw power from the Book of Prophecies' fragments during battle.

Dark Hide: The Dark Hide is a massive creature that resembles the Dark Thorn. It has a dark purple and black body with dark magenta spikes running down its back, as well as a "mane" of dark magenta tentacles around its head. Its tail has a dark magenta tip, and the Heartless sports four purple claws on each of its four legs. The most distinctive feature of the Dark Hide is its yellow eyes, which occasionally glow red. The Heartless also sports a jagged mouth, blue markings on its face and body, and chains around its forelegs. Its body is rather long and thin and, despite its massive size, the Heartless moves quite quickly. The Heartless is able to cloak itself in darkness, obscuring all of its features, save for its eyes, which glow bright red. It seems to be able to use its eyes to zoom in on the objects it looks at; from its perspective, everything has a very faint red tint. Glowing red veins are present around the sides of the Dark Hide's field of vision. The Heartless frequently creates disorienting after-images of itself as it moves, including red, green, and purple versions of itself.