Life Knife

The Life Knife — as coined by Ianto Jones — was a three-bladed knife (8 inches deep by 3 inches wide) used by Suzie Costello to kill people in order to test the resurrection gauntlet. The knife was associated with the glove as they were made of the same metal, and those killed with the knife were easier for the glove to resurrect. (TV: Everything Changes, They Keep Killing Suzie)

After Suzie's death, the knife was locked away in Jack Harkness's safe sealed with a "NOT FOR USE" tag. Torchwood Three, however, had to retrieve it to make the resurrection gauntlet effective on Suzie herself. Jack stabbed it into her stomach, and she awoke from death immediately. (TV: They Keep Killing Suzie)