The only way to get Thick Clubs is to take them from wild Cubone. Each wild encounter has a 5% chance of holding a Thick Club, and you can take it by either by catching the Pokémon or by using a stealing move like Thief.
You can only encounter wild Cubone after you’ve received the National Pokédex, and only on days when there is a mass outbreak of them. So this is a tricky item to get.
As for what it does: the Thick Club is a held item that doubles the Attack stat of the Cubone or Marowak holding it.
Acquiring Thick Clubs
Once per day there will be a mass outbreak (also known as a swarm) that randomly causes the encounter rate for a specific Pokémon to spike. These are typically Pokémon that aren’t found elsewhere in the game.
But you’ll need to obtain the National Pokédex before swarms will start breaking out.
The easiest method of finding out which Pokémon is currently swarming is to speak to the little sister of Professor Rowan’s assistant (Lucas or Dawn) in Sandgem Town. Alternatively, you can watch it on the Swarm News Flash TV program.
You can find Lucas/Dawn’s house directly south of Sandgem Town’s Pokémon Center.
Aside from telling you which Pokémon is swarming, she’ll also give you a Route number to check out.
If Cubone is swarming, head to Route 203 and start searching through the tall grass.
It won’t be long before you find one. Because a Mass Outbreak raises the chances of finding a Cubone in the wild from 0% to 40%.
Every Cubone you encounter will have a 5% chance of carrying a Thick Club, but you can improve the odds and make the process faster by putting together a dedicated item-farming team.
To take the item, either use a stealing move like Thief, or you can capture the Pokémon and remove it.
Afterward you can either finish the battle or flee. You will keep the Thick Club regardless.
Thick Club Details and Uses
The Thick Club is a held item that doubles the Attack stat of a Cubone or Marowak holding it.
With a Thick Club equipped, Marowak has the highest base Attack of any Pokémon in the game (160).
Paired with its high Defense and respectable Special Defense stats, it’s easy to see how a Thick Club offers an astounding new potential in a Pokémon that has been somewhat sidelined over the years.
Marowak’s abysmal speed and low HP mean that it’s still a challenge to use in more demanding battles.
But by compensating for weaknesses elsewhere on your team—perhaps by Baton Passing a few Agilities or Rock Polishes—you can turn the bone-wielding powerhouse into something truly fearsome.