There are different folk tales involving the devil and Jack o'Kent playing quoits here. This is paraphrased from Roy Palmer's The Folklore of (old) Monmouthshire (Logaston Press 1998) - "And when he got there he began playing quoits ...... threw three stones as far as Trelleck .... and he threw another but that didn't quite go far enough and it lay on the Trelleck road .... when it was moved so as the field might be ploughed;" A possible memory of a removed standing stone?
Probably more interesting is the sundial in the local church. Dated to 1689, along with a carving of the three stones, it states "HIC FUIT VICTOR HARALDAS" (Here Harold was conqueror), a memory in South Wales of Harold Godwinsson's successful campaigns there in 1055, 1056 and 1063.
Something is not right. This message is just to keep things from messing up down the road