A 'degrader' is a utility that will (in theory) downgrade your Amiga to a lesser spec.
There has been a pretty sophisticated one going by the name (if I remember correctly) 'degrader' which emulated ECS, slowed down the CPU, turned off fast ram etc.
With an A1200 you can degrade your Amiga from the early startup menu (hold both mouse buttons during a reset) and 'disable cpu caches' and select 'original chipset' (or something like that)
Running 'relokick' could help as well, that program loads Kickstart 1.3 onto ram to enhance compatibility. I remember that some old OCS games would need both a degrader and an older kickstart.
As Adolescent suggested using the 'assign' command in shell may also help. Assuming that you are copying the contents of the CD into a drawer in your harddrive, you have somehow to let the computer know where to look for them. That is because by default most games/apps etc will look in their parent folder (volume) of the medium they came with (whether disk, CD) for such things such as fonts, libs etc.
The command assign, hijacks all requests for a specific volume name (e.g. WrathDm:) and assigns them to a folder in your harddrive.
syntax:
assign [original path] [destination path]
e.g assign WrathDm: dh0:games/WrathOfDemon
replace WrathDm: with the CD's actual volume name (the name that appears in workbench as soon as you insert the CD) and the latter part with the full path of the drawer you copied the files onto.
Another tip: look into the CD's startup-sequence for any things it may be doing prior to loading the game.
I hope this makes sense. Good luck running it.