Ravenloft II: The House on Gryphon Hill shared structural elements with the original, including variable NPC goals and variable locations for key objects, so that Gryphon Hill plays differently each time. The module includes 11 cards which are used to randomly determine the vampire's identity and also the location of various items which need to be recovered as part of the plot, achieved through player/Dungeon Master interaction under the hypnotic trance of a player character. The module's plot features an artifact known as The Apparatus that switches a monster's personality with that of an ordinary townsperson; player characters, therefore, are uncertain about the true identity of the people they meet. The module also introduces Azalin the lich, who later became a major character in the Ravenloft campaign setting. This module is playable alone, or as a sequel to the original Ravenloft. It includes descriptions of the town of Mordentshire, as well as some haunted moors, and a manor house, all mapped in perspective like the original module.
Ravenloft's success led to a sequel in 1986 titled Ravenloft II: The House on Gryphon Hill. Although Tracy Hickman was credited in Ravenloft II, he had left TSR before the module was completed. The writing was done by David "Zeb" Cook, Jeff Grubb, Harold Johnson, and Douglas Niles, following the Hickmans' outline. Each writer pursued a different section of the module in order to meet the deadline.Clyde Caldwell, who had done all of the art for the original Ravenloft module, provided the cover, but interior art was done by Jeff Easley. The adventure is designed for first edition Advanced Dungeons & Dragons characters of levels 8–10. The adventure was 48 pages, and included a large color map and an outer folder. The pack includes a collection of player handouts, pre-rolled characters and a map, all of which match up with the booklet text, and an event chart, on which pre-set events have been logged day by day, and further DM arbitrated events are added.
Carl Sargent reviewed Ravenloft II in issue No. 87 of White Dwarf magazine, where he stated that it was a "strong sequel to I6 Ravenloft" and recommended it highly. He noted that the plotline is very complex, with interactions between PCs and NPCs being much more important, and key events help keep the action going and provide direction for the adventure. Sargent criticized the sequel for having over-the-top minor encounters, and warned that the complexity of the plot would require careful preparation. He did mention that the module includes play and time-keeping aids, and felt that the adventure was worth the extra effort. Sargent highly recommended Ravenloft II for "lots of monsters, plenty of roleplaying, lots of offstage action, items and crucial information to be gathered, and ... an excellent ending."Lawrence Schick also commented on the sequel in his 1991 book Heroic Worlds, describing it as "Gang-written just before deadline by the whole TSR design staff. The vampire Strahd returns in a gothic adventure of Things Man Was Not Meant to Know."
Tom Zunder reviewed Ravenloft II: The House on Gryphon Hill for the British magazine Adventurer #8 (March 1987). He declared that "this scenario is one excellent, if not the most excellent example of the genre. Following, as is so totally correct for the genre, the original Ravenloft scenario (I6), Tracy and Laura Hickman have quite superlatively re-created the style and atmosphere of the classic vampire tale, whilst at the same time never allowing the players a plot line transparent in simplicity." He comments that The House on Gryphon Hill is "not quite a sequal to the first adventure, nor is it a prequel, but rather a parallel story, and the idea of running both I6 and I10 in an interweaved nightmare would indeed make for a classic scenario". He felt that the interaction between the entranced player and DM "makes for rapid referee integration of the information, but since the opening days of the adventure are more involved than the inevitable false calm of all horror film beginnings, this should be no problem to do between sessions". He commented that the module is "well-written, with a clear and accurate plot description leading in to atmospheric and well-written chapters on the various major locations" and felt that the event chart makes "referee control and understanding of the scenario easy and clear". Zunder goes on to say: "The players' sense of realisty [sic] is excellently broken down, perturbing events are mixed with just enough sanity to never allow any security of expectation. The resolution is subtly tragic, with a mix of scientific and supernatural so necessary in this type of tale. The potential for running this scenario with any other RPG is enormous. Indeed, it would be especially suitable for a late 19th C or early 10th Century RPG, such as Justice Inc. or CoC. All in all, an excellent product, recommended for nearly everyone."