Sildonia is a sentient magic sword containing the personality and memories of an ancient Magic King. She ended up in Kail's hands after he cleared the Magic King's Great Labyrinth and claimed her as his reward. In the original timeline, Sildonia became both his weapon and a source of knowledge, fighting alongside him through various challenges.
When Kail finds himself back in time with his memories intact, one of his priorities is tracking down Sildonia again. He's determined to have her at his side once more. Once he does, Sildonia learns the truth about what happened—that Kail has somehow jumped back through time—and agrees to help him prepare for the coming Great Invasion, armed with the knowledge of what's to come.
Content compiled by AnimeList.moe from publicly available sources.
