The Dark Bow is a rare drop from Fire Giants.
The Dark bow has the ability to fire two arrows at once, and has a special critical hit ability costing 55% special attack increasing the damage the primary arrow deals.
The Darkbow has 10,000 durability, and requires combat level 20 (500 xp) to use.
The arrows fired from it do not reach the range of the crystal bow, however the Dark Bow fires two arrows at once, the second arrow deals less damage and travels with less velocity, meaning it doesn't go as far, but it is possible to hit two enemies at once with this special passive.
Each arrow normally does 18 damage, and each second arrow does 6, regardless of enchantments. The damage can vary high or low, going from 13-20 damage.
The special attack critical hit can deal up to around 35 points unaugmented.