Dead Demon Consuming Seal: Release

This technique involves invoking the Shinigami using a mask from the Uzumaki Clan's Mask Temple. From there, the act of preforming this technique can be potentially fatal, as the summoner cuts the Shinigami's stomach to release the trapped souls sealed within the Shinigami's stomach. Doing so, however, causes the same damage to appear on the summoner's stomach.

Orochimaru used this technique to restore his arms and free the souls of the previous Hokage, allowing him to reanimate them with Summoning: Impure World Reincarnation.

Trivia

 * Though this technique is not named by Orochimaru personally, the kanji for its name are readable in the scroll which details the technique.