What Pokemon evolves from a Damp Stone in Pokemon Pearl?

There is no such Pokemon item as a 'Damp Stone'. You may have gotten confused between two different items: The Damp Rock (an item found while digging in the Underground) is not an evolutionary stone. It is a hold item which boosts the number of turns in which the move Rain Dance lasts. This increases the power of Water-type moves and decreases the power of Fire-type moves for the duration of the move (which is extended with the aid of the Damp Stone). The Dawn Stone is an evolutionary stone which only evolves two Pokemon (as of Pokemon Diamond and Pearl). When used on a female Snorunt, the Pokemon evolves into a Froslass. When used on a male Kirlia, the Pokemon evolves into a Gallade. No other Pokemon can evolve from the Dawn Stone.