If you haven't played any of the entries in the "Kingdom Hearts" video game franchise then you may be confused by the Oathkeeper keyblade engagement ring. Basically, all you need to know is that a "keyblade" is a sword shaped like a key. This ring was made by Takayas, a custom jewelry shop that has previous experience dabbling in Disney-themed and nerdy engagement rings.
According to a Takayas blog post, a man named David commissioned the Oathkeeper keyblade engagement ring for his fiance, a huge fan of the "Kingdom Hearts" games. The resulting ring is subtly geeky, with only true fans of the series able to spot its inspiration. The keyblades form the band, and the center stone is meant to resemble the Wayfinder charm worn by Kairi, a character from the series.