"Darkness" (ダークネス Dākunesu) is an archetype of cards used by Nightshroud (whose own Japanese name is also "Darkness") in the Yu-Gi-Oh! GX anime. In the OCG, the archetype is exclusively supported by Boss Duel cards.
In the anime, it revolves around the "Darkness" Field Spell, swarming the field with "Darkness Necroslime" and recovering the controller's Life Points.
So far, the only "Darkness" monsters used by Nightshroud that have been released in the OCG or TCG (excluding Boss Duel cards) are "Darkness Destroyer", "Darkness Neosphere", "Red-Eyes Darkness Dragon" and "Red-Eyes Darkness Metal Dragon", although other cards can be supported by the anime-only support cards.