Effect
Extends duration of rain. (Hold)
Damp Rock increases the duration of Rain Dance from 5 turns to 8 turns when held by the Pokémon that sets it up. Those extra turns give rain-based teams more time to sweep!
This is key for dedicated rain teams. Swift Swim users and Water-type attackers get a lot more use when rain lasts 8 whole turns instead of 5.
Game:Polished Crystal