Demon Souls and Dark Souls are the spiritual successor to From Software's previous hardcore action RPG series King's Field, and both contain many references to it. Particularly, Seath the Scaleless in Dark Souls is a reference to Seath the white dragon in King's Field who is normally portrayed as a force of good.

What's even more interesting is that in King's Field lore, Seath's nemesis is the evil Guyra who also appears as the final boss in several of the King's Field games. He is described in the manual of King's Field II as:
"The Black Dragon who is opposed to the White Dragon, "Seath." Guyra broke a black crystal which controls the powers of nature. He created the "Moonlight Sword" to make his chosen warriors fight for his revival."

In the King's Field II, he appears as a one-eyed dragon. Guyra's appearance is very similar to the character introduced in the Prepare to Die expansion of Dark Souls: Black Dragon Kalameet, who is also a one-eyed black dragon.

Additionally, in the original King's Field, not released outside Japan, Guyra appears as a black dragon that "has lived in the forest and defended the people" since ancient times. This is similar to how Kalameet is fought in a forest in the past.