Lightbringer

Lightbringer was the legendary magical sword created by Karma Terrius, initially made to battle the Dark One in the First Dark War, but later expanded as a weapon for her Dotrist children in their various adventures. It was made of lightsteel, one of the strongest magical metals in the world, and was infused with a wide array of magic; it would amplify the magic of its user and could summon powerful light magic, in addition to many other skills. However, it would only allow those with Sentinel blood to use it, although Bailey Tracker later found a way to circumvent this.
The weapon was initially used by Karma Terrius during the First Dark War, where she used it to face off against the Dark One. Terrius, with the help of Creo Aedifex and Occasus Nix, defeated the Dark One, and continued to use the weapon for herself until the birth of her first son, Kori. Kori lived with his father in Therinsburg, taking the last name Tigenderth, and when he and his best friend Dernth Kelthshaw set out for Caworn, having discovered evidence pointing to the return of the Dark One. Tigenderth would eventually help unite Ecleinia, and as the chief commander of the Ecleinian forces in the Second Dark War, he wielded Lightbringer, eventually defeating the Dark One in combat and ending the war.
When Bailey Tracker, Terrius's second son, was born, after hiding him away with Garrick Tracker and Taryn Whitehawk, she brought the sword to Kelthshaw Academy, where Bailey would wield it. He used the blade in combat for his entire life, and also unlocked several secrets of the weapon- for instance, he was the one who discovered how to allow non-Sentinels to use it; Jessica Colwick and Fiona Daunton would both later use the weapon. Tracker also used it to kill the Dark One for good, and discovered that proper application could allow the sword to unleash nearly infinite amounts of energy, which he exploited to this end.