The Darkgnaw's shaft has a deep-grey edge which curves in at intervals, the inside fading from dark red to black from its base, which has several angled lines pointing toward the guard as the center bears a bright red line, stretching to the tip as it leads to an equally red rune marking. The teeth are axe-like, with the same coloration as the top of the shaft, an angled piece and several lines cut out, giving the illusion of teeth. The guard is a dark steel blue and has a hexagonal shape with numerous semicircles imprinted around it. The shaft inside is plain black.
The Darkgnaw's name, as well as its Japanese name, "Dark Biter", refer to the Keyblade's teeth, which resemble an actual toothed maw. "Dark" simply reflects the dark design of the Keyblade.
Darkgnaw is decent Keyblade that can be obtained rather early in Terra's story. It gives a decent amount of strength to Terra, and increases his magic, which in itself is considerably less than that of Ventus or Aqua. However, due to its short range, it can be troublesome to advance near enemies to hit them as that gives the enemies a better chance to get at Terra.
One recommended way to get the most use out of it is to first use either a Zero Gravity-type spell or a Magnet-type spell. Using the Zero gravity set will allow the enemy to remain suspended in the air long enough for Terra to get some decent hits in. The Magnet spells have the same benefit as the gravity spells, but also have the added bonuses of gathering nearby enemies together into one easy to reach spot, and doing damage to the enemies with holding them together. Using either of these methods provide ample time in which Terra can wail away at his enemies.