Life Knife

The Life Knife was a three-bladed knife used by Suzie Costello to kill people in order to to test the Resurrection gauntlet. (TW: Everything Changes) After Suzie's death, the knife was locked away in Jack's safe sealed with a "NOT FOR USE" tag. The knife is associated with the glove as they are made of the same metal, and that those killed with the knife are easier for the Glove to resurrect.

Stabbing the deceased with the knife can increase the connection with the glove even post mortem. The name "life knife" was coined by Ianto Jones. (TW: They Keep Killing Suzie)

They stabbed Suzie Costello in the tummy while she was stil dead to use the Resurrection Gauntlet on her to bring her back to life. (TW: They Keep Killing Suzie)