The glossary in Just Qvigstad’s book, Contes de Laponie, indicates that the Halde are invisible spirits. In one tale, “The Young Halde Girl,” the Halde manipulate an unsuspecting young shepherd. A man herding his sheep in the mountains of Kvaenangen sees a house with an open door appear suddenly in front of him. The old man and the girl inside chat with him and discover that he wants to marry, but no girl would have him. Seizing the opportunity, the Halde girl offers to marry him, but that he cannot live with them. If he returns in six months, she will go to him and be married in his church. She claims to know the catechism well enough to be baptized into the church.
He returns six months later, but doesn’t find the girl. He wanders the mountains for three days looking for her. A few weeks later, he sees her across the river, but she disappears before he reaches the other side. She appears to him in a dream, claiming that he was late to meet her the first time and too distracted by his fish to claim her from the river when she saw him a second time. She curses him for kissing her by making his mouth unable to taste his food.
From this story, we can conclude that the Halde were manipulative tricksters who could appear and disappear at will. They could take human form and inflict physical damage to the human body. They could also appear in human dreams.
In the story “The Halde,” there are two kinds of Halde—those that haunt the earth and those that haunt the waves. They are invisible. They are protectors of fish and assist the migration of salmon by moving dams, as recounted by a fisherman named Hello-Henrik who claimed to see a dam move several feet in the air without assistance one night.
Source: J.K. Qvigstad, Contes de Laponie, adaptation en français par Jacques Privat, Editions Esprit Ouvert, 2008, pp. 47-49, 59-60