Geralt encounters them for first time in Murky Waters as part of the Small Problems quest. There appear to be at least two tribes of griggs: the so-called "good" tribe and a "bad" tribe.
The good tribe inhabits the area between the currently ruined bridge to the fields and the riverbank, while the "bad" tribe has taken up residence in one of the deeper chambers of the crypt in the fields. Even the good tribe seems to have a rather mischievous streak. It seems that these tiny creatures let their opinions on the local bridge construction be known through nightly vandalism, much to the consternation of the local mason, Harn and his son, Pat. They also exhibit a marked appreciation for alcohol.
During main storyline of the second expansion for The Witcher 3: Wild Hunt these minuscule made their second appearance.
While Geralt is helping Sylvia Anna with founding three magic beans in the Land of Thousand Fables he can see small village where Griggs are living simple lives, collecting herbs, hoeing ground and cutting mushrooms bigger than them selves. But as witcher approach them, they run shouting to huts.
Although there are no references to the Griggs specifically in Anglo-Saxon culture and folklore, their model resembles a typical Irish goblin, of which the clover is a symbol and a reference. Nevertheless, the Griggs are somewhat similar to the Pookas or leprechauns, creatures of the Irish mythology.