DC Special 11 (March/April 1971) has a collection of stories from House of Mystery, under the title Beware...the Monsters are Here!, and a Neal Adams cover that evokes the first story in the issue, about gargoyles. It comes wedged between two other one shot concepts in this book. Stop! You Can't Beat the Law! from issue 10, contained mostly police stories from Gangbusters, although it also reprinted one of the tales from the Manhunters issue of Showcase, and a Fireman Farrell story from that book as well. Issue 12 cover featured Viking Prince, and reprinted three of his adventures from Brave and the Bold, as well as one each for Robin Hood, Golden Gladiator and Silent Knight.
Sergio Aragones provides the first and last pages of DC Special 11, entertainingly rendered, and featuring Cain.
This works very well, as a number of the House of Mystery stories reprinted also have Cain as their host.