In the 2017 series, Scrooge, as a young millionaire, rebuilt the castle from its old ruins as a gift to his parents, Fergus and Downy, who were living in poverty in Glasgow until that point. However, Scrooge used some druid stones during the castle's reconstruction that granted Scrooge and his parents and relatives and chosen close relations immortality, which they later see both as a blessing and a curse.
The castle is usually hidden behind the Mists of Dismal Downs,and is hard to visit with out it but every five years, the Mists part enough to make it easy for to be visit . Not much before the Spear of Selene incident, Fergus and Downy's grandchildren Donald and Della visited Castle McDuck, and Della hid Donald's hat in the dungeons as part of an elaborate prank.
Swamphole McDuck, an ancestor of the McDuck clan, built an elaborate system of tunnels under Castle McDuck to hide his treasure. To guard it, Swamphole also summoned a Demon Dog, that haunts the dungeons ever since. Later, Simon McDuck, an ancestor of the McDuck clan, hid the Knight Templar's treasure in the dungeons built by Swamphole. The dungeons are also haunted by a number of ghosts of the McDuck clan.