Nier: Caim and Angelus

Spoilers for Drakengard and possible spoilers for Nier.


 Nier is actually a spin-off of the Drakengard series, specifically of the first game's alternate ending. Of the game's five endings, two lead into separate games; Ending A leads to Drakengard 2 while Ending E leads to Nier. During the events of Ending E, the two protagonists, Caim and Angelus, confront the Queen Beast, resulting in a rift in reality that deposits the three of them in real-world Tokyo. After engaging in a bizarre, rhythm-based battle involving the use of song and magic, Angelus ultimately overcomes the Queen Beast, causing it to disintegrate, though she and Caim are in turn killed by fighter jets. 

 Over the course of several millennia, the effects of the battle ultimately lead to the storyline of Nier, due to it causing the spread of a lethal disease known as White Chlorination Syndrome (the theories by fans and websites suggest that this was caused either by the particles released by the disintegrating Queen Beast, or through the introduction of magic into a world where it didn't exist), ultimately leading to the initiation of Project Gestalt.

 However, despite the two games being within the same series, there is practically no in-game acknowledgment of Drakengard's events during the events of Nier, save for a vague reference from an NPC. While this works in regards to Nier's story being its own entity, I was kind of hoping for some easter egg from Drakengard, in this case a boss fight. It would have been interesting if Nier and his group encountered some echo of Caim and Angelus, possibly Shade-like in appearance while possessing the power of song used in Ending E, with Caim's moves resembling his fighting style and magical attacks. After the fight, the player could have been given Caim's sword as a reward.

 Even so, I strongly recommended checking out the Drakengard series. While its gameplay and graphics are dated by today's standards, the story, characters and history (provided through weapon descriptions) are what make it interesting.

Disclaimer: I do not own Drakengard or Nier.