The specific sentence of the ability is
allows the koldun to bring a piece of the Tempest into living world, conjuring a violent storm that throws anyone trapped within into a Harrowing.
For a wraith, a harrowing is a puzzle corrupted by their shadows designed to lead them to ascension
Without the influence of the Oblivion which is represented by the wraiths shadow harrowings are a form of tough love in the underworld forcing people to ascend.
The harrowing was originally a form of "tough love" in the Underworld - intended to help wraiths come to terms with their own deaths when they weren't willing to come to terms with it themselves. The Underworld has been corrupted by Oblivion since that time,
Living beings don't have shadows until they die since shadows are created by the influence of Oblivion in the underworld which means there is nothing to influence harrowing in a bad way.
Living beings also haven't died yet. Harrowings are also often constructed in forms of a persons regrets so instead of making you come to terms with your death it would make you come to terms with your mistakes.
Combining all of these it can be assumed that a harrowing triggers a form of seeking similar to one a mage goes through when they get closer to ascension.
As a final note: Orpheus addicts have shadows of their own because of the pills influence. As such their harrowings would be corrupted.