This was a puzzle/platformer in the Lemmings vein. You controlled 5 imps, each with a unique skill. IMPostors! sold well enough for the authors to begin working on a sequel, but the sequel was abandoned.
Interview with the main author, Stephen McGreal, is in issue 2 of SAM Revival magazine, which also covers the limited work on the sequel.
IMPostors! was re-released on issue 74 of Soundbyte diskzine.
In January 2020 IMPostors! rights were purchased by Colin Piggot of Quazar along with other Mungus Software titles.