This achievement applies to The Bard's Tale II: The Destiny Knight.
Saradon's story is a new addition from the folks who created the remastered The Bard's Tale trilogy and directly connects with the changes to the Dreamspell.
Start by searching the house up in the far north eastern section of the wilderness map - N45 E29. Search the body and you will find a WardStone.
Once you've got the WardStone, you can go down to Philippi (N13 E15) and go to its north eastern section to find an iron gate that the WardStone will open for you (at N12 E13). Note that the Master Key will not work here; it has to be the WardStone.
Then head up north and into Saradon's Workshop! The achievement pops as you head inside, though if you spend some time getting through his teleporter maze and into the workshop proper, you'll find the clues necessary to get the words in order to later get the Dreamspell.