The Survival Knife (サバイバルナイフ, Sabaibaru Naifu?), also known as Lightning's Knife, or Keepsake Knife in Final Fantasy Record Keeper, is an important item in the Final Fantasy XIII trilogy. It is an ornate present that Lightning received on her twenty-first birthday from her sister Serah. "OP148" is engraved on the disc, albeit in the Cocoon alphabet.
Serah Farron purchases the Survival Knife as a gift for her sister Lightning's twenty-first birthday. At Lightning's birthday dinner, Serah reveals that she has become a l'Cie, as well as that she intends to marry her boyfriend, Snow Villiers. These words greatly upset Lightning, who refuses to believe them. After an upset Serah leaves the house with Snow in pursuit, Lightning opens the gift box Serah had given her and discovers the Survival Knife within. It is as she beholds Serah's gift that Lightning realizes her sister had been telling the truth, but at this point, it is too late to make amends.
During her journey through the Gapra Whitewood with Hope Estheim, Lightning hands the boy the Survival Knife in order to boost his confidence; she also does this to give herself more of an incentive to protect him.
In Palumpolum, Hope is placed under Snow's care, despite the fact that he dislikes the man. After the two l'Cie defeat the Ushumgal Subjugator, a powerful PSICOM military unit, Hope confronts Snow about the death of his mother and attempts to kill him with the Survival Knife. Before he can do this, a PSICOM missile hits the building they are standing on, throwing Hope off the edge. Snow catches the boy in midair and uses his body to shield him from the fall. When Hope comes to, Snow returns the Survival Knife to him and tells him the story behind it. At this point, Snow and Hope make amends. The Ushumgal Subjugator attacks them once again, however, and it manages to knock out the wounded Snow. Hope attempts to defend Snow; Lightning and Oerba Yun Fang come to his aid, and after the Ushumgal Subjugator is destroyed, Hope gives the Survival Knife back to Lightning.
After the catastrophe, Lightning disappears and Hope finds the Survival Knife under the base of Cocoon's crystal pillar. He hands it to Serah, who keeps it in her room in New Bodhum until Noel Kreiss arrives and asks her to aid him in his search for an artefact, which can be used to open the Time Gate that crashed on the town's outskirts. It is called Lightning's Knife in the inventory.
During their search for the artefact, Serah and Noel come across the Survival Knife, which, to Serah's surprise, has been polished. The two believe this to be the result of a paradox, but in actuality, the Survival Knife had been polished by Gadot, who claims Lightning would be mad if she found out the Survival Knife was "poorly maintained."
Stretch and forget the past. Walk down your chosen path to...the light.
The Survival Knife is a trade accessory needed to craft Lightning's exclusive level 100 weapons. Along with other accessories needed for level 100-exclusive equipment, it can be found in The Dragon King's Gateway or traded for three Megalixirs.