Blockula (Blåkulla in modern Swedish, translated to "Blue Hill") was a legendary island where the Devil held his Earthly court during a witches' Sabbath.
Children would be convinced to perform the ride after being given "a Shirt, a Coat and a Doublet, which was either Red or Blew," and being asked if they wanted to attend a faraway feast; if they didn't accept the invitation they would be forcibly brought along, regardless.
The place or House they met at, had before it a Gate painted with divers colours; through this Gate they went into a little Meadow distinct from the other, where the Beasts went, that they used to ride on : But the Men whom they made use of in their Journey, stood in the House by the Gate in a slumbering Posture, sleeping against the Wall.The events of the night were started by having each witch cut their finger to sign the Devil's book in blood, and undergoing a mock baptism in which they swear their soul to the Devil.In a huge large Room of this House they said, there stood a very long Table, at which the Witches did sit down : And that hard by this Room was another Chamber, where there were very lovely and delicate Beds.The Devil's most esteemed witches would sit closest to him, at the head of the table, whereas the children would stand by the door.
And he bids them believe, that the day of Judgment will come speedily, and therefore sets them on work to build a great House of Stone, promising, that in that House he will preserve them from God's fury, and cause them to enjoy the greatest delights and pleasures : But while they work exceeding hard at it, there falls a great part of the Wall down again, whereby some of the Witches are commonly hurt, which makes him laugh, but presently he cures them again.
They observe farther, That their Childrens Breasts grow cold at such times; and they take sometimes a burning Candle and stick it in their Hair, which yet is not burnt by it.