Yes, XzavierHyde is correct. Years ago Cinemaware allowed you to download all of their Amiga ADF game files from their website, but for reasons I do not know they pulled those downloads many moons ago. I have every Cinemaware ADF game file from them because of their generous givings at that time. I run them in the Amiga Forever emulation suite and they run flawlessly unlike what I have been reading in the GOG reviews of Defender of the Crown.
I am curious if those that have purchased DofC from GOG if the ADF file is included? It seems reasonable you could get DofC running perfectly with some emulation tweaks which is a snap in Amiga Forever's front end.
Update: Got my answer. It runs perfectly with UAE which is a joy to use using the Amiga Forever package which I highly recommend supporting. Cloanto has done an amazing job over the years.
http://www.gog.com/forum/defender_of_the_crown/would_this_run_in_an_alternative_amiga_environment