Amusingly enough the Huldra's method of ghost-busting is quite familiar. Bind the spirit in place with ethereal shackles and then suck them into the containment unit that is their hollow interior!
Sadly we didn't get to see it.
"People?" Freddy echoes, sounding rather surprised. "You mean... you haven't noticed...?"
He glances around, sniffs the air a few times, twitches one of his ears, then shakes his head. "There might be one wraith here. But that wasn't the apparition I was after. These are ghosts, echoes of the living. Imprints of memory forced to repeat the last things they did in life for eternity."
He makes a sweeping gesture with one hand. "Some can remember a little longer than others. But I'm sure that if the living people left this place it wouldn't be long before the dead forgot you were ever here. They're only lost memories. No more a person than an old book is."
Then another gesture and a wisp of fox fire appears in his hand. Appears and resolves into an almost doll-like shape of a wind-up dancer. The teeny apparition begins to leap and spin and wheel about. "Besides. Eating the ghosts doesn't destroy them. It just means they're bound to me rather than whatever location they're haunting."
Hopefully that person with the vines doesn't thwack him. Things would go down-hill fast. And the person babbling at him is regarded with a sour look. "Nothing I've said is a lie," he replies. And he's totally telling the truth! But is he telling the whole truth? That's another question to answer!
And it's probably worth noting that the Huldra uses no magic. Magic is very much the domain of Warlocks and Witches. Not the craft of a beast of Discord such as himself! Nor do generic resistances to illusions, up to and beyond the likes of True Sight, cut through the glamors he weaves. Only a sprig of Allheal can reveal the full truth behind a Huldra's deception.
Good thing Allheal is a weed that can be found pretty much anywhere.