“I ask you, are you my master?” – Saber
Servants are like super familiars. They are spirits heroes and monsters from present, past, and the future that are summoned with the power of the Holy Grail to participate in the Holy Grail War. They are summoned by mages known as Masters. As servants have real identity that may be recorded somewhere, they should hide their true name, some does it better than others, here is looking at you Gilgamesh. Hiding their name as well as categorizing, Servants fall under certain classes. There is the Standard classes, and there are a few that defies the standard. Standard Classes include: Saber, Archer, Lancer, Rider, Assassin, Caster and Berserker.
There will be some spoilers ahead. And I will be mainly focusing the main series, so things like Fate/ Extra, Grand Order, andso on are just brief mentions.
Historically considered to be the best class. Saber class Servants are known for being extremely powerful in close combat, very well balanced, and sturdy in every sense of the word. Many of the Sabers shown through out the Fate franchise are from the Knights of the Round Table from the Arthurian legends. As many Sabers are royal knights, they have formal or royal-esque manners and stubbornness. Saber is one of the Three Knight classes.
Notable Sabers: King Arthur, Mordred, Gawain, Nero, Lancelot
This class Servants are known for their independent behavior as well as marksmanship (obviously). Archers are not ideal for close combat; however, they are apt in long range as well as reconnaissance.Due to their independent nature, many Archers tend to be sarcastic and cunning. Archer is one of the Three Knight Classes.
Notable Archers: Gilgamesh, Robin Hood, Emiya Shirou
This class Servants are masters in close combat as well as mid range combat. Lancer is one of Three Knight classes.
Notable Lancers: Cu Chulain, Vlad III, Diarmuid Ua Duibhne, Scathath
Like their name suggests, this class of Servants are unparalleled in mobility. The method of transport used by Riders can range from legendary horses, chariots, ships, and so on. Rider is one of Four Calvary classes.
Notable Riders: Iskander, Medusa, Achilles, Francis Drake.
Not known for direct combat, Assassin class Servants prefer stealth and information gathering. Assassin in the Fourth Holy Grail War (Fate/Zero) is an interesting case in that a group of spirits act as a singular Servant. Assassin is one of Four Calvary classes.
Notable Assassins: Hundred Faced Hassan, Hassan of the Cursed Arm, Kojiro Sasaki, Li Shuwen.
Caster classes are made of extraordinarily powerful mages. They do not like close combat and prefer to do things further away. Caster is one of Four Calvary classes.
Notable Casters: Medea, Gilles de Rais, Nursery Rhyme, Archimedes
Is probably the strongest in terms of physical prowess alone. This class sacrifices their sanity and reason for more power. Heroes who qualify for other classes, say a Saber, can become Berserkers to further amplify their stats. While generally being “mindless” they do seem to follow their “nature”. What I mean by that is FSN’s Berseker acts as a guardian towards Ilya, almost as is he is protecting his daughter. While the Berserker from Fate/ Zero is driven by wrath towards Saber. Berserker is one of Four Calvary classes.
Notable Berserkers: Heracles, Lancelot, Spartacus, Frankenstein’s monster
That is the basics of the stand classes. But with many Fate series, there are classes that go beyond the seven.
Also known as the Servant of Vengeace is an atypical Servant. In the main story, during the Third Holy Grail War, Angra Manyu was summoned as Avenger in okace if a Berserker. And Avenger is resposible for corrupting the Holy Grail so that unheroic spirits can be summoned as Servants as well as making it evil…
Notable Avengers: Angra Manyu, Medusa, Count of Monte Cristo.
To be frank, I have almost no knowledge of this class as it seems to be only from Grand Order up to this point. She is a Demi-Servant, a person fused with a Servant. She has a big shield…. that is all I’ve got.
Notable Shielders: Mash, Galahad (kind of).
Ruler is another Servant I am not too entirely familiar with. Ruler’s responsibility is to ensure that the Holy Grail War goes on in the interest of the Holy Grail. They are to take no sides and work for the Grail. Rulers also have Command Seals for other Servants.
Notable Rulers: Joan of Arc, Shirou
There are more Classes, but I wanted to only touch on the main ones and couple of non-standard ones, I hope you understand. Please feel free to expand on the info here or call out my mistakes!