The Pisaca in the dungeon in the Duke's Archives are actually humans captured by the Channelers for Seath's experiments, explaining why these creatures drop a fairly consistent supply of Humanity. Two in particular each drop a different Miracle. When considering the fact that Rhea of Thorolund's Hollow can be found in the dungeon after all her Miracles are purchased, and the fact a corpse in the dungeon is wearing the Maiden Set that Rhea wears, it can be speculated that the two docile Pisacas are former Maidens, and that Rhea was going to receive the same fate.

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.

When originally announced, the game was titled "Dark Ring". The name was changed to Dark Souls because "Dark Ring" can be seen as a euphemism for an anus.

This was the second time the name changed. The first time was also unintentionally risque; "Dark Race".

The character most commonly known as Snuggly the Crow or Sparkly the Crow is not a crow at all. She is actually a hawk named Hawk Girl and the more common names were actually created and propagated by fans.

Lost Izalith was originally going to be a swampy area like the bottom of Blighttown. However, FromSoftware didn't want it to be a swamp and so it was redesigned to be a lava field, but the team couldn't completely redesign the place the way they wanted to due to time constraints.