Here's why it doesn't work:
* Mercy is a noun, meaning compassion or forgiveness. It doesn't describe how something happens.
* Adverbs typically end in "-ly" (e.g., happily, quickly), or have other forms (e.g., very, quite, never).
To express the idea of mercy in an adverbial way, you can use phrases like:
* Mercifully - This is a common adverb derived from "mercy" and means "with mercy" or "in a merciful way."
* With mercy - This phrase directly conveys the idea of mercy and can modify a verb (e.g., "He treated her with mercy").
* Compassionately - This adverb focuses on the compassion aspect of mercy.
* Kindly - This adverb can also express a similar sentiment of forgiveness and understanding.
Example:
* Instead of: "The king showed mercy to the prisoner."
* You could say: "The king mercifully spared the prisoner's life."