Amazon’s upcoming adaptation of Neil Gaiman and Terry Pratchett’s “Good Omens” may center on the relationship between an angel (played by Michael Sheen) and a demon (played by David Tennant), but the show strives to reach out to everyone.

“It’s about us — our flaws, that trust and belief in humanity. It’s probably what brings us here,” series star David Tennant said at SXSW Saturday.

“Good Omens” co-author and series showrunner Neil Gaiman explained that the origins of Sheen and Tennent’s characters were originally designed to be one, but rather than a good vs evil balance in one being, it was Pratchett who split the two, creating the angel Aziraphale as a meeker enigma living amongst the humans, and pulling out Crowley as his balanced evil counterpart. For the series, Gaiman also wrote in the Archangel Gabriel (played by Jon Hamm) to be an antagonist between the unlikely duo who team up to save the world.

Gaiman was the first to describe previous attempts at bringing “Good Omens” to the screen as too complex, despite always being able to picture it working somehow. He worked on ideas with Pratchett initially, and when his co-writer fell ill, Gaiman said Pratchett told him, “You understand it, and you have to make this.”

Gaiman did, explaining his process as, “Everybody being trusted to do their own thing, at their own level.” In addition to his big name cast, Douglas Mackinnon came aboard to direct all six episodes, something that the group considered an unusual circumstance for television today but an important one.

“Everybody walked away from this show thinking we did something special,” Mackinnon said.

When prodded for information on whether they’d consider bringing another season of “Good Omens” to the screen, Gaiman assured the audience that the upcoming six-episode season would be it. At the behest of Sheen, Gaiman did reveal the name of what the sequel would have been called had he and Pratchett been able to write one, though: “668: The Neighbor of the Beast.”

“Good Omens” launches May 31 on Amazon.