Resurrection gauntlet

The resurrection gauntlet was a metal gauntlet (also known as The Glove and given the joking name of Risen Mitten by Ianto Jones), that had the ability to bring the dead back to life for a limited time. It was also believed to have either fallen through the rift and recovered by the Torchwood Institute or been recovered in a church by Captain Jack Harkness; both gloves were destroyed in the end, whether there are more gloves remains unknown.

History
The right gauntlet was recovered from Cardiff Bay by Torchwood 3 circa 1967. (TW: Everything Changes) It had a strange but unspecified connection to the "Life knife", an alien artefact made of the same type of metal. (TW: They Keep Killing Suzie) Jack Harkness said once he suspected the glove was not lost like most things that fall through the rift, but was disposed of, guessing the original owner wanted to be rid of it. He also could not blame them either for wanting to be rid of it.

The gauntlet could revive the dead, though only for a few minutes before their second, permanent death. The length of time someone came back depended on the users empathy, in other words someone like Gwen Cooper could bring a person back for a few minutes but someone like Owen Harper would not even get a twitch out of a corpse. Jack put Suzie Costello in charge of testing the glove. Costello became obsessed with the possibility of being able to bring people back to life, though only for minutes at a time. She began buying goldfish in bulk and killing them to test out the gauntlet. (WEB: torchwood.org.uk) The Glove was more effective on recent, violent trauma victims. Suzie Costello began to murder residents of Cardiff with the Life Knife in order to improve her proficiency in using the glove (TW: Everything Changes). She conceived an elaborate plan to use the glove, the Life Knife and the gauntlet to bring herself back from the dead, permanently. (TW: They Keep Killing Suzie)

Following the exposure of Costello as a murderer, she shot herself in the head, killing herself. The Glove was placed in Jack's safe and sealed with a "DO NOT USE" tag. Jack theorised that whoever had "lost" the glove wanted to lose it. (TW: Everything Changes)

Costello had already set into motion murders committed on her behalf so that Harkness would revive her, enabling her to come back to life, permanently. Gwen Cooper was the only Torchwood 3 team member at that time with the degree of empathy required to operate the glove without Suzie. When the glove was used on Suzie, Gwen's life force was slowly drained from her into Suzie and she even began developing the same wound as Suzie in the back of her head where Suzie's was. The only way to break this connection was to destroy the glove, which Toshiko Sato did, saving Gwen and killing Suzie again. However, Ianto Jones pointed out that "gloves come in pairs", implying that there may be another glove. (TW: They Keep Killing Suzie)

After Cooper's love, Rhys Williams, had died, she briefly asked whether they could use the glove to make him come back to life. (TW: End of Days)

After the death of Owen Harper, Jack used the help of a psychic to locate the other, left glove (Ianto had remarked that gloves come in pairs), in order to do the resurrection of Owen Harper for the standard of two minutes so the team could say their goodbyes. However, Owen did not die after two minutes. Unlike Suzie, Owen remained clinically dead, showing no signs of life, but remained fully animate and cognitive and he was also not drawing power from Jack (the person who revived him). The team soon discovered that a strange energy was slowly transforming Owen's cell structure. The team researched the second glove, and found that its use in the past allowed the 'grim reaper' or 'death' to enter the world and if death then takes 13 lives, it can remain in the living world. The team tried to stop Owen's transformation by injecting embalming fluid into his body, but the second glove became animate and stopped them by attacking Martha Jones, and drains her life away, leaving her at the age of 80. The second glove was destroyed like the first, with a gunshot, but its remains then turned to a powder that formed death's physical form. (TW: Dead Man Walking)

Characteristics
Suzie's research showed that the glove was slightly radioactive and that the glove possessed "low psych levels" which allowed it to directly respond to brain activity. It was later established that it had an empathic link in the form of energy with its wearer, which showed up on video cameras like "a rope from [the] heart to the glove" and that transferred the life force of the wearer to keep the dead alive. (TW: They Keep Killing Suzie)

The second glove turned out to be fundamentally different from the first. Instead of using the 'lifeforce' of the wearer to reanimate the dead, it tapped into the power of the personification of death from the 'otherside' to reanimate the subject. In this sense it can be seen to be a yin/yang relationship between the two gloves. The first keeps a balance by exchanging one life for another, but the second uses an unnatural force to create a type of 'zombie'. The second glove itself also seems to be far more sinister in nature, is able to move under its own power, and possesses a limited amount of intelligence (as shown in it's attack on the team when they tried to stop the transformation process); however, this may have been the entity, from which the glove drew its power, manipulating it. Strangely, while the glove was hostile with most, it was calm with Ianto, and disturbingly seemed to sit in his hands rather than being held by him. Whether this was just a glitch, the glove playing innocent or something else remains to be seen. (TW: Dead Man Walking)