A Relic (レリック Rerikku) is a Lost Logia that appears as a red jewel with immeasurable power, similar to Jewel Seeds in having a serial number. Relics are normally associated with disaster and Jail Scaglietti intends to use them for his own plans. Relics are the main focus of the plot of Magical Girl Lyrical Nanoha StrikerS.
During the events in StrikerS, Hayate Yagami's Riot Force 6 is tasked with monitoring and containing all relics being smuggled into Mid-Childa so as to keep them out of the wrong hands. The danger posed by the Relics is demonstrated when Dr. Scaglietti devises means of fusing an individual's Linker Core with a Relic, which simultaneously gives the victim immense magical power (technically turning them into an Artificial Mage) and places them under Scaglietti's complete mind control (as in the case of Vivio and Ginga). An individual thus infused with a Relic can be freed if subjected to a powerful magical bombardment, such as Divine Buster or Starlight Breaker, which destroys the Relic without permanently harming the victim.
Lutecia Alpine and Zest Grangaitz were identified as "Relic Weapon Experiments" (レリックウェポンの実験体 Rerikku Weapon no Jiggentai) and were searching for relics with specific serial numbers (Lutecia was searching for Relic No. 11). They were working with Jail Scaglietti in an agreement where they would find relics for him and if the relics they found aren't the ones they want, they would give them to Scaglietti.
Relics are normally contained in boxes marked with the relic's serial number.