Hidan is a member of the Akatsuki and is partnered with Kazuku. He has exceptional skill wielding his triple-bladed scythe. He is immortal and has a jutsu that allows its victim to experience whatever injury Hidan suffers. These two things combined have turned him into a sadomasochist.
Hidan is originally from the Hot Springs village. Once a powerful ninja village, they became pacifists that had forgotten war, but Hidan desired strife and took out his aggression on the village. Thanks to this he was found by the Jashin religion and was their first successful experiment, being granted with immortality in return for killing others.
Hidan is first introduced as a member of the Akatsuki with their first task being hunting down and capturing the two tails Jinchuuriki, being held within Yugito Nii of the Hidden Village of the Clouds, with his partner, Kakuzu. She puts up a strong fight, having fully mastered control over the Two Tailed Nibi, but Hidan is able to dispatch of her with a secret technique that is only later revealed. They handed her body over to Zetsu, and with his partner being a bounty hunter, quickly followed this up by heading into the Land of Fire to destroy a temple and collect the bounty on the head of the head monk Chiriku.
What they didn't know was that Chiriku was a close associate of Asuma, who was also part of a task force designated to track down the Akatsuki and take them out. Shortly after Asuma's team is successfully able to find them, and they begin to battle Hidan while Kakuzu decides to stay out of it until he's needed. Hidan is able to get a drop of Asuma's blood on his scythe, and follows this up by licking it off. Once he has done this he begins to draw a circle on the ground in his own blood. Asuma doesn't know what he's up to but he knows it can't be good, so he uses a fire breath technique to try and defeat him, but its too late. After the fire hits him Hidan is completely unharmed, but now Asuma is the one burned. When the smoke clears Hidan reveals himself to have completely changed skin, taking on the appearance of a skeleton. This is the technique he used to defeat Yugito, being immortal he cannot die from any harm but now the person whose blood he drank will suffer whatever damage is inflicted upon him.
Hidan begins to stab himself, creating the same injuries on Asuma until he can no longer move. Shikamaru believes he has figured out the trick to Hidan's power, as he uses his Shadow Jutsus to force him to walk outside of the circle, severing his link with Asuma. Believing they now have the upper hand Asuma takes one of his blades and cuts off Hidan's head, thinking no one could survive that, but they were wrong. Even this isn't enough to kill Hidan as his head begin yelling for help, which causes Kakuzu to finally enter the battle. Kakuzu sews the head back onto the body, and then distracts the other members of the team long enough for Hidan to step back into the circle of blood, and stabs himself in the heart. Support arrives to help Asuma's team escape, but it is too late, for Asuma has already been killed.
Hidan is ordered to next hunt down the Kyubi, Naruto. He and his partners arrive in the village, only to find that Kakashi Hatake has teamed up with Asuma's old students, Shikamaru, Ino, and Choji, to stop them once and for all, and this time Shikimaru has a plan. After a quick battle between the duo, in which it is learned that Hidan is not the only one close to immortality, as his partner Kakuzu has five hearts, all of which grant him incredible powers and can fight seperately of himself, Shikamaru leads Hidan into the forest away from his partner.
Once safely away Shikamaru stalls him as long as he can, but finally Hidan is able to cut him with his scythe, taste his blood, and begins the ritual again. He stabs himself in the heart to finish it quickly, but Shikamaru reveals it wasn't his blood he drank. Kakashi was able to cut Kakuzu in their fight, gathering some of his blood in a glass, a glass that Shikamaru broke on Hidan's scythe. In other words, Shikamaru just tricked Hidan into stabbing his own partner in one of his five hearts.
Shikamaru then begins his counterattack. He leads Hidan into a trap surrounded full of exploding tags that he wraps Hidan in. The tags explode, destroying the ground beneath him and ripping Hidan's body to pieces. Hidan falls into the hole in the ground, while his head still yells up at him from this grave, promising he'll make it out one day and bite Shikamaru to death. These are his last words as Shikamaru then causes the hole to cave in, burying the immortal forever.
Immortality - Thanks to the Jashin cult, Hidan has been granted immortality. Even if his head is detached from his body it can still talk and survive. However it is believed that he can still die from a lack of nutrients since he still needs to eat.
Jashin Curse - Hidan is able to use a type of ritual which requires him to ingest his opponent's blood, which then allows him to synch his own body to theirs. This means that any harm brought upon himself will be experienced by his opponent so long as he stays inside the ring he draws on the ground with his own blood. Considering that Hidan is immortal, this creates an instant kill attack. When he performs this ritual his body changes to look more like a skeleton.
Three Blade Scythe - Hidan uses a giant three bladed scythe that greatly increases his reach and makes it easy for him to collect the blood he needs for his ritual.