"What was in that friendship potion or whatever the love of my life gave me?" Vincent questioned while acting sick.
On their way to the Dullahan village, Awa had told Vincent about a mixture of poison her people knew to make. Additionally, all Dullahans carry a small leaf packed with this poisonous power, but Awa's leaf with poison was lost or left with her clothes.
The hostage poison was colorless, slightly spicy, and odorless when added to water. The finely crushed ingredients would dissolve in water making the water difficult to distinguish between ordinary water and poisoned one.
The Dullahan's victims would know the poison's name as the friendship potion, while the real name was the hostage poison.
The victim would suffer from the condition of losing a small percentage of their strength while also having an additional hidden effect.