Truman and Giorello's ongoing Dark Horse series Conan the Cimmerian is coming to an end, but will be followed by the four-issue miniseries, it was announced at C2E2 in Chicago.
"With Scarlet Citadel, Tomas and I will bring a whole new level of craftsmanship and concentration to the title," Truman told CBR.
"I can't wait to see what Tomas cooks up - he'll be able to lavish even more detail on to each page. I think Scarlet Citadel will be a monumental thing, visually."
The comic will be based on Howard's short story of the same name, which deals with one of Conan's adventures following his ascension to the throne of Aquilonia.
Dark Horse also announced 12-issue Conan: Road to Kings miniseries, written by Roy Thomas, who in 1970 became the first writer to pen a Conan comic.
Truman added that there may be more miniseries to follow, saying: "By all means. Fetch them hence."
King Conan: The Scarlet Citadel will debut later this year.