The Curse Technique: Death Controlling Possessed Blood is the exclusive technique of Hidan and his primary method of killing his opponents under Jashin.
The technique requires two special conditions: One being that Hidan must have drawn an insignia of Jashin on the ground in his own blood, to which he must remain in the centre for the technique to function properly. The other being him to acquire and ingest the blood of his intended victim. Once ingested, his skin then turns black with white markings which makes him look like a skeleton, a symbol of absolute death. This serves as the link between him and his victim.
Once his sacrificial ritual takes place, the victim is linked with Hidan until he either steps or is forced out of the circle. Any kind of injury that Hidan inflicts upon himself (or the injury they inflicted on him) is reciprocated on his target, be it a mere scratch to a pierce in the heart. If Hidan is forced to step out of the circle, the link is temporarily broken and the victim is set free, but only as long as Hidan has stepped out of the circle's reach. Basically, this technique makes Hidan a living voodoo doll.
Hidan's immortality is due to the "successful experiment of the Jashin religion's secret technique", so he can fatally torture his opponents in any way he desires without killing himself, and he clearly enjoys the pain as well. However, he does indeed complain that it hurts like one normally does in pain, after he finished off Asuma.