There's a malicious creature found in Northumberland and Durham England who must be a close friend of Shucks. This vile old spirit is a shape-shifter called the Brag. Unsuspecting travellers may encounter Brag as a lonely horse or donkey idling along an isolated road, quiet field, or windy moorland. Thinking the animal is wonderfully tame, the poor traveller will climb onto the animals back, only to be taken on a wild ride until thrown into a cold pond or thorny bush in total terror. The nasty shape-shifter then runs off laughing at the scratched, drenched, and otherwise humiliated soul who is now thoroughly bewildered about what just happened.
The Brag is very similar to the Phooka of Ireland, and Kelpie of Scotland, two more shape-shifting equines often associated with lakes and other waterways. The Kelpie, a sometimes black, sometimes white horse, is actually worse than the Brag, since instead of merely laughing at its victim, it drowns and consumes them. The Phooka, a glistening black horse with yellow eyes, will abduct children and throw them over a steep cliff, possibly into water below. Since water is a traditional gateway to the underworld, the Brag and its cousins may be remnants of a pre-Christian equestrian cult. It's also interesting that brag is the word for ghost or goblin in northern England.
The Brag does not alway appear as a horse. At times it will take the shape of a calf wearing a white neckerchief, a headless man without a stitch on, or four men carrying a sheet. An old article about the Brag can be found HERE.