House of Mystery #188 (On Sale: July 9, 1970) has a cover by Neal Adams.
This issue introduced American comic fans to the amazing pencil and ink artwork of Tony DeZuniga in its first story, "Dark City of Doom" written by Gerry Conway.
Next is a Cain's Gargoyles one-pager written and drawn by Sergio Aragones, a Page 13 one-pager by Joe Orlando and Sergio Aragones and a Cain's Game Room one-pager by John Albano. In a few years John Albano and Tony DeZuniga would team up to create western anti-hero Jonah Hex.
This issue ends with "House of Madness" drawn by Bernie Wrightson.
The entire issue was reprinted in Showcase Presents: The House of Mystery Vol. 1 TPB.
Edited by Joe Orlando.