‘Heide’ existed where Drangleic does today on the western coastline. Whether Heide refers to a kingdom or was just a name for the land is not clear, for no records date back far enough to tell. All that is known is that the Way of Blue has its origins in Heide, and that Heide was later subsumed by the sea.
From this description we can only guess at the origins of Heide. The city certainly draws strong influences from Anor Londo in terms of style and architecture. The statues with the eagle heads are clearly modeled off those of Gwyn found in Anor Londo, and the eagle is a bird said to represent the sun in reality, so this is a strong hint these statues were made to honor a god of the Sun. Taking this evidence into consideration, it may be that Heide is very ancient indeed and that it was constructed around the time of Anor Londo. It should not be ignored that the Way of Blue originated in Heide, and this covenant is closely related to the Blades of the Darkmoon which uses a Blue Eye Orb to invade the world of sinners and punish them. The Blades of the Darkmoon were a covenant under Gwyndolin, son of Gwyn and run out of Anor Londo. These similarities seem to indicate that Heide either is Anor Londo, or what was left of it, or perhaps a city founded by those who had known Anor Londo.
A notable difference between the Way of Blue and the Blades of the Darkmoon is that while the Way of Blue does have an emphasis on carrying out punishment, it is also a covenant designed to protect those who cannot protect themselves. Perhaps this difference reflects the more human influence on the covenant’s priorities? The apostles of Blue gather in the grand cathedral of Heide, a place that used to be bustling and it would seem the cathedral is the base from which the Way of Blue operates out of. If this is the case, then the Kingdom or land of Heide appears to have been ruled by a somewhat benevolent leader who valued worship of the gods, perhaps these ‘gods’ even resided within the cathedral, having direct communication with their subjects.
Many of the Knights of Heide wielded lances. These weapons are normally wielded by mounted knights, and it takes considerable training to handle one on the ground. This descriptions indicates that the knights of Heide perhaps did ride mounts. It is likely these knights waged war against someone else’s forces. The Heide knights encountered in the game have helmets and armor pin-cushioned with arrows. This certainly confirms someone was hostile towards the knights of Heide, but may also give further evidence to the idea that these knights rode mounts, as it is easier to take down a mounted knight with arrows than a sword.
If the knights did ride mounts into battle, then who did they ride against? We perhaps have our answer in Vendrick’s Dragonriders. We know that together with his Dragonriders, Vendrick crushed the former inhabitants of Drangleic and built his kingdom upon their graves. The legendary Dragonriders straddled not horses, but wyrms. This is very interesting, as it seems clear that these Dragonriders with deific strength would be able to take on the knights of Heide, despite the special alloy found in their weaponry that made it very durable. There are two other facts to take into consideration when theorising about the fate of Heide. The first is that Drangleic’s forces attempted to imitate the special alloy used in Heide weaponry, and the result was the similar bradden steel. This certainly seems to indicate a rivalry between the forces. The second is that within Heide is found the game’s one and only Dragonslayer, called the Old Dragonslayer. This warrior appears to have risen to the challenge of defending Heide against aggressors, and likely aggressors who fought with dragons. Finally, if this was not evidence enough towards the idea that Drangleic fought against Heide, it should be noted that Drangleic’s crest is a pair of twin dragons (perhaps representing Aldia and Vendrick), and in Scholar of the First Sin we even see a dragon from Drangleic’s Dragon Aerie outside the Blue Cathedral.
So if Heide did fight against Drangleic in combat, how did it end up subsumed by the sea? From the presence of the remaining Heide Knights in game, it would seem that Drangleic was not victorious solely by military strength, but rather the forces of Drangleic caused the flood of Heide. It is interesting to speculate on how this may have happened, but what seems possible if not likely, is that Heide was built behind a bulwark as New Orleans is today, to keep out the sea, since it was built on the coast. Should those bulwarks be broken the city would be at the sea’s mercy. So it is possible that unable to gain the upper hand against Heide’s forces, Drangleic broke the bulwarks and flooded the city.