OVA
Description
D's Left Hand is a sentient symbiotic entity that resides within the palm of the vampire hunter D, appearing as a human face on a small, often lumpen mound of flesh. It is a being of a type known as a Countenanced Carbuncle, a species of normally parasitic organism. However, this particular entity is unique among its kind, possessing abilities and a relationship with its host that set it apart. The origins of Left Hand remain largely mysterious, though it is implied within the narrative that it was once one of the Barbarois, human-monster hybrids who served in the personal retinue of the Sacred Ancestor, the immensely powerful first vampire. Some hints even suggest the Sacred Ancestor experimented on it to enhance its powers before it became bonded to D.

In terms of personality, Left Hand functions as a polar opposite to its stoic and taciturn host, D. Possessing the gruff, wisecracking demeanor of an old man, it is far more outgoing, expressive, and prone to sarcasm and humor, often needling D with constant commentary and jokes. While its temperament is usually lighthearted and it prefers taking the path of least resistance, Left Hand can become utterly serious and display a will of steel when a dire situation demands it. This moral compass is complex and somewhat inconsistent; on some occasions, Left Hand can be colder and less willing to help those in need than D, while at other times, it shows more warmth and compassion. Despite their frequent disagreements, the two share an affinity for combat tactics and work in perfect tandem, as though of one mind, bound by a deep and ancient friendship.

The entity acts as D's sole permanent guide and companion, providing a critical reservoir of knowledge about the lost culture and technologies of the vampire Nobility. It rarely reveals itself to anyone other than D, and at all other times, its host's left hand appears entirely normal. Beyond its role as a confidant and advisor, Left Hand possesses a vast array of mysterious powers that prove invaluable. These abilities include psychometry, the power to hypnotize weak-willed individuals or induce sleep, diagnose medical conditions, and accurately gauge the supernatural power of an enemy, sometimes even surpassing D's own senses.

One of the most significant of its abilities involves the consumption and manipulation of the four classical elements: earth, water, fire, and air. Left Hand can consume these elements, storing them within a pocket dimension that serves as its stomach. By converting the consumed elemental energy into life force, it can revive D from normally fatal injuries, such as a stake through the heart. Beyond resurrection, consuming specific elements grants unique powers: earth allows for a killing strike; water permits it to freeze objects; fire enables it to breathe intense flames; and air allows it to propel objects at extremely high speeds. By consuming all four elements simultaneously, Left Hand can empower D to a godlike state that rivals even the power of the Sacred Ancestor himself.

The entity is incredibly ancient, being over ten thousand years old, and its development over the course of the story shows it to be nearly unkillable. It has survived being separated from D and even being completely destroyed, with the ability to resurrect itself. Its only known, and possibly temporary, weakness is an unusual susceptibility to extreme cold, which can render it sleepy, though this has not proven to be a consistent or permanent flaw.