From the introduction:
In 1981, TSR published the module named Castle Amber with the module code X2. It was written by Tom Moldvay and illustrated by Jim Holloway, Harry Quinn, Jim Roslof, Stephen D. Sullivan, and Erol Otus. This 32-page booklet had an outer folder containing a map of the castle. An AD&d 2nd Edition boxed set sequel adventure, Mark of Amber, was released for the Mystara line in 1995. In 2004, for the 30th anniversary of the Dungeons & Dragons game, Dungeon magazine ranked this module the 15th greatest adventure of all time. This conversion guide allows DMs to run the original module with 5th Edition rules and provides a reference sheet for encounters.
A 20+ hour adventure for 3rd–6th level characters
Note the original module is required for the use of this conversion product.