Black Lacrima

Black Lacrima (真黒魔水晶 (ブラック・ラクリマ), Burakku Rakurima lit. Pitch-Black Magic Crystal), also known as simply Umbra (本影, Shadow), are man-made Lacrima, considered to be a perfect anti-thesis to Red Lacrima, but are few in existence, and aren't commonly used.

Description
Unlike Red Lacrima, which are natural, albeit rare in numbers, Black Lacrima is a special type of Lacrima, that is created typically by scientists who study Magic. A prime example being Lamia, who created the Black Lacrima as a counter measure against Red Lacrima. As their name implies, they are pitch black in color, or rather, "lack color".

If Red Lacrima is the polar opposite of Lacrima, then Black Lacrima would be considered the central inbetween. It is capable of absorbing Magic, like normal Lacrima, but doesn't negate any existing Magic, like Red Lacrima. However, Black Lacrima cannot produce Magic or spells, due to it being unstable, because of its purpose and usage.

It can only be used by experienced Mages who are capable of manipulating their Magic power with great enough proficiency, and is utilized by molding the Black Lacrima itself, allowing it to change form, size and freely create barriers, or weaponry. The shell of the Black Lacrima is incredibly thick, which is what grants it its black color, and thanks to its thick layer, it is immune to Red Lacrima, thus it cannot be destroyed by it, or negated, unlike normal Lacrima.

However, because of the changing form of Black Lacrima, it has no actual form, thus, is untable and spells cannot be utilized in conjuration with it, leaving mostly as a weapon.

The true power of Black Lacrima, is the fact it doesn't exert any Magic power when utilized, since it only changes shape, thus, allowing Mages to fight a safe distance away, and without exerting any Magic power in the process, making it have infinite usage. Its size also varies, but typically, Mages can grant it more power in order to increase its size, or absorb the power from it, to replenish their own Magic. However, it is difficult, due to the thick layer, and requires alot of effort to go through without breaking it.

However, it is not without weakness. The most common weakness being that the Black Lacrima can be destroyed by a strong enough attack. Even vaporizing it and leaving nothing behind. This includes physical attacks, as with great enough force, the Black Lacrima can break, making the magic power inside of it leak out and make it useless.

Another weakness is that, while Black Lacrima can be used for long range attacking, being manipulating while the user simply takes a distance away, a powerful Mage can override a Mage's control over their own Black Lacrima, and use it against them. However, this is typically overcome by a Mage "branding" their Black Lacrima, making it identify only the Mage that branded it as its controller, via a stigma implanted onto it.

Regardless, the Black Lacrima's shapeshifting prowess grant it almost infinite amounts of possibilities. Being usable as weapons, or even armor for combat. It all simply depends on the user's imagination and creativity.

Trivia

 * Black Lacrima is partially inspired by the Truth-Seeking Ball from Naruto, but also meant to be a way to give Mages an advantage against Red Lacrima.