Blue Lantern Corps is the archetype for a group of parallel world, doppelganger, or otherwise related characters. These characters include:

• Saint Walker (16)

Part of Geoff Johns vision for the Green Lantern Corps mythology was an entire spectrum of coloured Lanterns each representing a different emotion. The Green Lantern Corps were naturally linked to green/willpower. Sinestro’s Qwardian ring was expanded into an entire yellow/fear Sinestro Corps. The smallest and most select of the new Corps was the Blue Lantern Corps, an off-shoot of the Green Lantern Corps founded by the exiled Guardians Ganthet and Sayd. Johns described Blue Lanterns in Wizard #207:

The Blue Lanterns are extremely rare. They are extremely powerful and each one has an ultimate destiny. They’re also each chosen in a very different manner from any other Corps. They’re sought out and chosen by other Blue Lanterns and are brought to the world of the Blue Lanterns, and Ganthet and Sayd (the former Guardians and creators of the Blue Lantern Corps) talk to them. They spend time with Ganthet and Sayd in the thick jungles of the planet and get everything laid out. They learn every single thing about themselves and their role as a Blue Lantern. Then they decide if they want to become a Blue Lantern or not.

These new Lanterns Corps were driven by hope and had a quasi-religious feeling to them. They could almost be described as chaplains compared to the Green Lantern’s infantry.

Johns explained the concept to his artist Ethan Van Sciver who then had to design the basic look and feel of these new characters. He started with the Corps symbol and the look of their costumes:

While the Sinestro Corps were hideous aliens with jagged stalactite shapes on their uniform, the Blue Lanterns suits were based on rounded shapes, and only the noblest, kindest-looking creatures were eligible.

Blackest Night Tales of the Corps #2 (Sept 2009)

In sketching the basic model of the Blue Lantern costume Van Sciver created a placeholder alien to wear it (because somebody had to be wearing it as it was being designed). Ethan told Newsarama how that placeholder alien became Saint Walker:

Saint Walker was a drawing I did at an airport, just to draw an alien. And Blue Lanterns were the first costumes I designed, so I just put him in costume. And I showed it to Geoff just as a way to demonstrate the suit. I said, “Don’t worry about the alien. He’s no big deal.” Geoff loved the alien and said he was going to come up with a name for him. Now, I thought he was going to come up with some goofy alien, fake comic book name like Bleech or something like that. But he called him Saint Walker, which to me, is divine. I never would have thought of it. I need to ask him where that name came from. I’m dying to know.

Saint Walker and a few other Blue Lanterns were briefly shown in a double page spread in Green Lantern (vol. 4) #25 (vol. 4) #25 (Jan 2008), but the character didn’t appear properly until almost a year later in Final Crisis: Rage of the Red Lanterns #1 (Dec 2008).