Shadow Bond is an aura-based ability inherently found only in the Shadow Drake. It is an evolved gene gained from Shadowsongs, which are closely related to Shadow Drakes and commonly breed with them. The way this ability works is that Shadow Bond affects the bearer's aura: if two dragons with this aura are near each other, their auras recognize and strengthen each other whether the dragons are aware of it or not. The result of this is that the Shadow Drakes become stronger as long as they are within range of each other. As Shadow Drakes are meant to work together, while this ability is indiscriminate among bearers of Shadow Bond, it rarely works against the Shadow Drake as they are usually allies anyway. It cannot be controlled and only affects individuals with Shadow Bond.
The Shadowsong's version of this is slightly different but works similarly. It also affects the aura, but is controllable as long as the Shadowsong knows it can control the ability, and strengthens the aura of the target. The target does not need to have a similar power in order to benefit from the Shadowsong's aura. Unlike the Shadow Drake's ability, if the Shadowsong is knocked unconscious then the ability is null, a defense mechanism so that if the Shadowsong cannot control what the aura targets, its enemies won't benefit from the aura themselves.