It once happened that Paracelsus was walking through a forest, when he heard a voice calling to him by name. He looked around, and at length discovered that it proceeded from a fir-tree, in the trunk of which there was a spirit enclosed by a small stopper, sealed with three crosses.
The spirit begged of Paracelsus to set him free. This he readily promised, on condition that the spirit should bestow upon him a medicine capable of healing all diseases, and a tincture which would turn everything it touched to gold. The spirit acceded to his request, whereupon Paracelsus took his penknife, and succeeded, after some trouble, in getting out the stopper. A loathsome black spider crept forth, which ran down the trunk of the tree. Scarcely had it reached the ground before it was changed, and became, as if rising from the earth, a tall haggard man, with squinting red eyes, wrapped in a scarlet mantle.
He led Paracelsus to a high, overhanging, craggy mount, and with a hazel twig, which he had broken off by the way, he smote the rock, which, splitting with a crash at the blow, divided itself in twain, and the spirit disappeared within it. He, however, soon returned with two small phials, which he handed to Paracelsus—a yellow one, containing the tincture which turned all it touched to gold, and a white one, holding the medicine which healed all diseases. He then smote the rock a second time, and thereupon it instantly closed again.
Both now set forth on their return, the spirit directing his course towards Innsprück, to seize upon the magician who had banished him from that city. Now Paracelsus trembled for the consequences which his releasing the Evil One would entail upon him who had conjured him into the tree, and bethought how he might rescue him. When they arrived once more at the fir-tree, he asked the spirit if he could possibly transform himself again into a spider, and let him see him creep into the hole. The spirit said that it was not only possible, but that he would be most happy to make such a display of his art for the gratification of his deliverer.
Accordingly he once more assumed the form of a spider, and crept again into the well-known crevice. When he had done so, Paracelsus, who had kept the stopper all ready in his hand for the purpose, clapped it as quick as lightning into the hole, hammered it in firmly with a stone, and with his knife made three fresh crosses upon it. The spirit, mad with rage, shook the fir-tree as though with a whirlwind, that he might drive out the stopper which Paracelsus had thrust in, but his fury was of no avail. It held fast, and left him there with little hope of escape, for, on account of the great drifts of snow from the mountains, the forest will never be cut down, and, although he should call night and day, nobody in that neighbourhood ever ventures near the spot.
Paracelsus, however, found that the phials were such as he had demanded, and it was by their means that he afterwards became such a celebrated and distinguished man.
The Legend of Paracelsus – Folk-lore and Legends: Germany