The Castle theme is one of LEGO’s primary themes first introduced in 1978 and based around medieval life with castles and knights. It is currently the third longest-lived theme in LEGO history. Over the years it saw numerous changes thus introducing various fantasy elements.
Black FalconsThe Black Falcons were an early faction of LEGO's Castle theme and were introduced together with the Crusaders in 1984 when LEGO relaunched their Castle theme after the discontinuation of the first knights faction. The Black Falcons name is not actually official as the name comes from the set 6074 Black Falcon's Fortress. The Black Falcons subtheme and faction was discontinued in 1992.
Black KnightsThe Black Knights were a faction of the Castle theme introduced in 1998. A total of 13 sets were released containing 3 major castles. Most of the castles and fortification where colored black and their symbol was a wyvern dragon. While The Black Knights subtheme was discontinued after 1994 the crest was still used in later sets.
CrusadersThe Crusaders were one of the factions of LEGO's Castle theme introduced in 1984 along with the Black Falcons.
Dark ForestThe Dark Forest subtheme released in 1996 consisted of only 3 sets and were primarily only available in North America. Dark Forest is a somewhat continuation of the Forestmen subtheme which was discontinued in 1990 as it reused the same crest and used other environment structures such as forest hideouts.
ForestmenThe Forestmen were introduced in 1987 and represented a faction in the Castle theme. Forestmen consisted of 7 sets including various hideouts and fortifications as well as simple carts and was discontinued in 1990. In the LEGO Catalogs, the following description was used; The Forestmen are a merry band of skilled archers. They enjoy good food and good times.
Fright KnightsThe Fright Knights where part of LEGO’s dive into the fantasy realm for the Castle theme. The Fright Knights faction of sets featured dragons and witches and a dark sorceress. A giant bat emblem was the crest for Basil the Bat Lord and his forces of fright. New elements for this theme included bats, chains, crystal balls, and Basil's winged helmet.
KingdomsThe Kingdoms subtheme was introduced in 2010 and ran until 2012. Kingdoms takes place in a medieval time period with sets in a European style from the 15th century and is based off of two human kingdoms fighting each other, the Lion Kingdom and the Dragon Kingdom.
Lion KingsThe Lion Knights were released the same year as the Black Falcons in 1984. As with the Black Falcons, LEGO never officially named this faction for some time, although catalogues in the United States and Australia used the name Lion Knights while Canada used Lion Crest. The Lion Knights were in open conflict with the Forestmen, as shown by several catalog settings.
Royal KnightsThe Royal Knights were one of the factions of the Castle theme introduced in 1995. Royal Knights was the first theme that introduced a minifigure portraying a king with a real crown. Most sets were released during its launch. The following year saw only two new sets. The Royal Knights had two minor guest appearances in sets of Dark Forest and Fright Knights.