Starting with Fate/Stay Night, super-powered entities known as Servants are summoned according to seven classes - Saber, Archer, Lancer, Rider, Caster, Assassin, and Berserker. These classes exemplify a Servant's particular strengths, which will vary according to which class they are summoned in. For example, a Servant summoned as a Saber will behave differently if they are summoned as an Archer.

As the franchise continued, more classes known as Extra classes were added. Fate/Hollow Ataraxia introduces the Avenger class. Fate/Apocrypha introduces the Ruler class. BB and Sessyoin Kiara introduce the Moon Cancer class in Fate/Extra CCC, but it was not properly named as such until Fate/Grand Order. FGO likewise introduces the Shielder, Alter Ego, Foreigner, Pretender and Beast classes.

This pool comprises images containing at least two Servants throughout the series who belong to the same class. Likewise, large group images consisting of Servant pairs summoned in different Holy Grail Wars under the same class can be included here. Cosplays are acceptable as long as they represent the same class.