Nier is a franchise with very different and unique characters. In Nier Automata, we were presented with many robots that mimicked human society and had several philosophical issues. In Nier Replicant, we have artificial bodies that gain consciousness and do not understand the philosophical issues that are presented to them, dooming their species and humanity. In both games, in order to enjoy it, players have to be ready for a high dose of Yoko Taro's Nihilism.
When introducing Weiss, the same idea behind the franchise is presented. With an amazing voice actor behind him, this book has a lot of personality and interesting lines. Weiss can be fun and funny in his own way, but that's only because his cynical behavior and careless bluntness are funny from the outside. Either way, there is a lot more to Weiss that what can be seen on the surface, just like anything else in this franchise.
10 He Was A Person
Grimoire Weiss is a Gestalt trapped in a book. Since a Gestalt is generally the living soul of a human that was separated from its body, this means that Weiss had a body and was a human being at some point. The name of the Grimoire, which is also known as The White Book, does not seem to have any connection to whom he was before.
Weiss was recruited when he was only a 10 years old kid to fight the Legion, one of the many details some people miss in Nier's plot. He says at some point that he never got used to doing it.
9 He Was Fond Of Another Grimoire
When he was fighting the Legion as ordered by the Hamelin Organization, he met a girl who was also being used by the same people who had recruited him at such young age. Since he became very much fond of her, he would put more effort into being successful in certain activities and battles so she wouldn't have to suffer and endure as much.
Unfortunately, this story did not have a happy ending. Eventually, both Weiss and the girl were turned into Grimoires. She became the mute Grimoire Rubrum. Maybe the tragedy in Weiss's life is what turned him into this cynical, blunt gestalt that can be quite funny.
8 He Was One Of The Thirteen Kids Recruited
Apparently, the Hamelin Organization did not put all their chips in Weiss. The organization would turn kids into fighters due to some kids having greater success with the drugs manufactured by them. Those drugs would make them more resistant to the White Chlorination Syndrome.
Not only was Weiss not the kid recruited by them, but he also was not the only kid turned into a Grimoire against his will either. There were other 12 kids who were made to fight each other and most likely lied to about the outcome of this competition.
7 What Happened To Him Is Not Clear
At The End of Nier Replicant, Grimoire Weiss loses his physical form when he decides to use all his power to restrain the Shadowlord. That was the only way Nier would have a shot against his Gestalt self and apparently caused Weiss to lose his physical form.
It is not clear what happens to Weiss after that. He is incorporeal, but not dead as many shades. He might not be a shade yet but it is not clear if he will ever be. And even if that happens, it does not mean he will go mad.
6 He Is One Of The Most Popular Characters
It is undeniable that some characters are very popular in the Nier franchise. Emil is one of them for sure. Kainé is also very popular among Nier fans, but Weiss is even more popular than both of them, losing only to Nier and Yonah.
It seems that a popularity pool was conducted during a Niconico live stream when Nier Automata was being promoted. The Producer, Yosuke Saito, was the one conducting the live stream and he was very surprised to see Weiss as the third most popular character.
5 He Can Act As A Fan
This is a weird thing about the character. Weiss can flip his pages quickly, which causes him to effectively act as a fan. This has no use to him, personally, but it does please the ones in the receiving end of the wind.
It seems that Weiss used to dislike doing this very much at first. Then, it granted him a lot of praise. This act was so well received and earned him so many praises that Weiss got to a point where he did not mind doing it anymore.
4 He Was Always Meant to Be Constantly Around Nier
Due to technical constraints, the Original Nier Replicant did not feature the exact combat that was envisioned by the creators at first. That had an impact on the flow of the combat, making the player stuck while Weiss was casting a spell. Weiss used to only appear when the player was casting a spell, now the book is always hovering close by.
In Nier Replicant ver.1.22474487139, Weiss feels much more independent too. The player can hop around while charging a spell and attacking with a melee weapon. This makes Weiss feel more powerful, and also like a different entity, which is what Ito envisioned. There's even a way to fist bump Weiss now, helping to make him be a character more than an accessory.
3 There Is A Reference To Him In Nier Automata
Through downloadable content for the sequel of the franchise, Nier: Automata, we get to see everyone's favorite grumpy, old Grimoire again. Unfortunately, he is not a fully fleshed character this time. Either way, this is a nice addition for those who are fans of both games and miss him since playing Nier Replicant or Nier Gestalt.
Grimoire Weiss can be used as a Pod appearance in the second game. The text for his Pod Model says that he is: "A high-capacity device used in the Gestalt Project. It exudes a vague aura of pompousness."
2 He Is Also In SINoALICE
In this game, it is required of the players that they buy Grimoire Weiss in order to unlock the Nier/Sorcerer job class. He comes with 300 magic crystals during the collaboration event that was named RepliCant x SINoALICE. This is a crossover that features many unconfirmed lore plots to the Nier Replicant timeline. Most likely, it is just fan service and lore excuses to make the crossover possible but not canonically real.
In battle, Grimoire Weiss lowers the enemy's physical magic attack power and physical attack power when used. However, Weiss targets one or two foes randomly when doing so.
1 He Is Voiced By Liam O'Brien
There was absolutely no one who could have been better to voice Grimoire Weiss. His witty personality, along with his edgy behavior, fits perfectly with the kind of characters that Liam is known for creating and lending his voice to.
Liam is the voice of Gaara, Doctor Strange, Red Skull, and Red XIII in Advent Children. He is also the voice of War in Darksiders and Yasuo in League of Legends. Being experienced in playing emotionally distant, cool, edgy characters who sound amazing, it seems there would never be someone better fit to be Weiss.