Kasteel Donker is a member of the Belgian quadrupel family. These are strong, sweet to bitter, dark brown beers where the malt predominates. They were inspired by the beers of the Trappist brewers. It is a full-mouthed, malty beer with touches of caramel, coffee and chocolate coming from the roast malt. The sweet initial taste is quite surprising. Further tasting shows this beer to be intriguingly complex.