The LEGO minifigure knights in the initial Castle sets feature movable visor pieces with eye slits. They also wear a coat of arms (either a tunic or breastplate). Since no horse specific elements are developed yet, the knights´ horses are built entirely of bricks. In 1984, the LEGO Group releases new Castle sets with castles that are more realistic and knights that more accurately depict the Middle Ages. The new sets feature many new elements such as one-piece horses, horse saddles, helmets with fixed visors, feather plumes, waving flags, bows and arrows. The sets also mark the debuts of several new factions of knights bearing symbols on their shields. The biggest factions are the Crusaders and the Black Falcons. There is no obvious king – the first royal LEGO minifigure with a crown is launched in 1995.

During the 1980s the Castle theme isn’t just about castles and knights. Also, civilian LEGO minifigures such as a peasant or a blacksmith are featured introducing a medieval hat that is still one of the defining characteristics of the theme. Civilians are also represented at the Armor Shop, set no. 6041, and the Guarded Inn, set no. 6067, from 1986. A new faction is added in 1987 with LEGO Forestmen. The Forestmen are outlaws who dwell in hideouts build into hollow trees and rocks. The Forestmen are a merry band of skilled archers who enjoy good food and good times. Their opponents, the LEGO Wolfpacks, are introduced in 1992 as robbers and bad guys.

In 1992 the LEGO minifigures in the Castle theme are diversified by printed faces adding more personality to the characters than the simple smiling faces.

The Dragon Masters are introduced in 1993 moving the Castle theme into the realms of fantasy and mythology by adding dragons and wizards. The Dragon Master army is a small regiment of knights and guards led by the wizard Majisto. Majisto is noteworthy for his pointed hat, his glow-in-the-dark magic wand, and his long white beard, all new elements that year. He is also the first LEGO minifigure in the Castle theme to have a proper name - in fact, Majisto is one of the first minifigures to have a name of any kind. Fantasy is back in 1997, when LEGO Fright Knights bring along witches and dragons, as well as an eerie looking villain with a bat as his symbol.

In 2000, LEGO Knights’ Kingdom is released with King Leo leading the knights who fight against an army of bandits being under the command of Cedric the Bull. King Leo’s followers are housed in a castle, while the Bulls live in the Dark Forest. This is the first Castle theme to feature a complete royal family with King Leo, Queen Leonora, Prince Edward and Princess Storm. Four years later LEGO Knights’ Kingdom II is released featuring colorful knights with individual names and personalities battling against the evil knight Vladek. The theme is a radical departure from any previous Castle themes being more action-oriented and having superhero abilities.

The LEGO Castle theme is relaunched in 2007 followed by LEGO Kingdoms in 2010. Both themes return to a more traditional and realistic medieval setting repeating earlier established fantasy elements such as dragons and sorcerers, but also adding new ones such as Skeleton Warriors, Trolls and Dwarves. Whereas the Castle theme from 2007 includes many fantasy elements, the Kingdoms theme is based on two human kingdoms fighting each other, the Lion Kingdom and the Dragon Kingdom. The Lion Kingdom is led by the Lion King, and the Dragon Kingdom’s leader is unknown, although sometimes implied to be a wizard. In 2013, the Castle theme reappears replacing the Kingdoms theme. It features historical and fantasy elements combining some aspects of its predecessors. The 2016 launch of Nexo Knights saw a larger focus on storytelling and digitalization than seen before in a Castle theme, creating an elaborate universe of good and evil characters.