The Fate series is one of the most expansive in anime, branching out into movies, shows, games, and novels galore. There are so many creative spinoffs from different artists tackling different subjects and genres that it can be exhausting figuring out what to check out. Fate's universe actually lends its lore to the other works of Kinoko Nasu from the 90s and early 2000s such as Tsukihime and Garden of Sinners, before the release of Fate/Stay Night. Fans have dubbed this shared lore the "Nasuverse" named after Nasu himself, but the universe has branched off into numerous works from many authors.
Fate/Stay Night has been hugely successful and Studio Ufotable's adaptations have been their crowning achievements, alongside other entries such as Fate/Zero. Nowadays, Fate/Grand Order has dominated the public perception of the franchise, itself having numerous anime adapting its lore. But there are so many facets of this universe to approach when making new stories, so much so that the idea of a canon timeline is practically nonexistent. It's the reason getting into the franchise can be so confusing, but there are certain stories that aren't just great, but that exceptionally explore specific parts of the world.
The Pre-requisites
This list is made with the assumption that people looking into these spinoffs are already somewhat familiar with Fate or have watched one or more of the most popular iterations. Gen Urobuchi's Fate/Zero for one, and Fate/Stay Night, notably Unlimited Blade Works, for understanding the general rules of the world.
If one so chooses, the Heaven's Feel movies are also well-made and the Studio Deen adaptation from the 2000s is underrated. The point of this is to explore a few of the side stories best suited to expanding the fantasy world while offering great stories. And a few of them can be enjoyed without any prior knowledge.
Lord El Melloi II's Case Files
Fans of Fate/Zero will love this light sequel to the events of that story as this anime follows Waver Velvet, one of the masters from Zero, all grown up. When Reines, the niece of Waver's deceased former mentor makes him a proposition, he ends up taking the El Melloi name and becomes a teacher of Modern Magecraft Studies.
The show follows Waver and his assistant Gray taking on different investigations, using his intuition to solve mysteries tied to the magical world. Meanwhile, Waver dreams of joining the next holy grail way to reunite with Iskandar, with whom he shared a deep bond during the events of Fate/Zero.
If it isn't clear from the description alone, this series is a phenomenal treat for fans of Zero, but it stands on its own well enough for its unique and fun mystery setup. The Fate universe has an impressive skill among its modern fantasy peers. It goes to great lengths to establish the magical society is governed in a way that's believable.
Not only are the powers on display awesome, but the hierarchies, bureaucracy, politics, and scheming make the world feel very believable, even with such fantastical plotting. Lovers of good world-building and modern fantasy will find plenty of pleasing imagery in conjunction with a solid soundtrack and gorgeous animation.
The Garden of Sinners (& Tsukihime)
Consider this a twofer, but Garden of Sinners having the superior animated adaptation certainly makes it the main contender here. It's an occult dark thriller series about a woman named Ryougi Shiki investigating the supernatural alongside her boyfriend as well as a former mage turned freelancer.
Yes, it's another show about investigations, but the aesthetic, setting and overall feel are completely different. While Lord El Melloi II is a consistently fun fantasy, Garden of Sinners is a darker tale set within the dingy alleys of 1990s urban Japan. Japanese urban horror can be especially atmospheric and this series of films is the definition of "a mood."
It started as a novel series that, unfortunately, has never been officially translated and brought to the west. However, while there are certainly fan translations, the easiest way to experience Garden of Sinners is through the animated film series available on Blu-ray or through Crunchyroll.
As for the second half of this duo, Tsukihime is the visual novel that Garden of Sinners was basically the prototype of. The main character is a boy named Shiki Tohno who has the same power as the Shiki from Garden of Sinners, just more powerful. It's dark in the same ways the other series is, but being a visual novel it has more routes and more of a "pick your favorite girl" meta game.
Tsukihime actually had a remake released on PlayStation and the Nintendo Switch, but it has yet to be released in the west. Hopefully, that changes soon, but in the meantime, Garden of Sinners is readily available to give a taste of what Tsukihime started as.
Fate/Strange Fake (... But Technically Fate/Apocrypha)
This last suggestion is an odd one because it isn't actually an anime, nor a visual novel. It's a regular novel, in fact, and a light novel series at that. Fate/Strange Fake tells the story of a fake Holy Grail War held in a city in the United States in Nevada.
It's an ongoing light novel series that's had a ton of buzz on account of the complexity of its narrative and the game of chess between the adversaries that makes any Fate story great. The problem is that it hasn't been translated and brought to the west officially either.
It's especially amusing that a very similar story came out back in 2017. Fate/Apocrypha, rather than being about seven heroic spirits fighting over the holy grail like the original, was about two armies, seven spirits each, going to war. Strange Fake has a similar premise, but with considerable differences in how events play out.
The community tends to come to the consensus that Strange Fake is a better story than Apocrypha and a fan poll by AnimeJapan revealed that the manga version was the second most requested to be adapted to animation. Unfortunately, since the novels are not completed, it likely won't get an anime for a while.
Fan translations of the earlier novels are available on the internet, and considering the quality of the animated commercial for the sixth novel's release, an anime is inevitable. For those craving more of the battle of minds and mettle that makes Fate so compelling, this series might just be worth reading a book for once. And if that's too daunting, you can always watch Apocrypha on Netflix.
Lord El Melloi II's Case Files and Garden of Sinners are available for streaming through Crunchyroll. Fate/Apocrypha is available for streaming through Netflix.