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When held by a Pokemon, reduces the power of a damaging Normal-type move used against the holder by 50%. Consumed after use. Natural Gift becomes a 60 Base Power Normal-type attack when the user holds this Berry, but the Berry is consumed after use.
Why exactly you would want to weaken damage from Normal-type moves is anyone's guess. The only place you will really find dangerously powerful Normal-type moves are on sweepers that require it for STAB, such as Staraptor or Snorlax, in which case it is better to find a way to counter those Pokemon directly.
Receive from Fennel on first visit to Dream World—however, you only get one of the seventeen damage-reducing Berries, and this event cannot be repeated. If you do not receive a Chilan Berry in this way, you must trade for it using Share Shelves in the Dream World.