There are several evolutionary items you’ll need to find to evolve your Pokémon. One of these items is Protector. The Protector is a holdable item which when held by Rhydon while it is traded, will cause it to evolve into Rhyperior. This walkthrough will show you where to look for Protector in Pokémon Brilliant Diamond and Shining Pearl. There are two locations where you can find Protector.
#1 Route 228
Head to Route 228 and go past Ace Trainer Jose’s house. Protector is lying in a pit that you can climb up with your bicycle at the beginning of the route. Make sure to take your bike out to go back up the hill after you’ve retrieved it. National Dex is required to access and navigate and explore the entire area.
#2 Battle Tower
Protector is available for purchase at the Battle Tower for 5 BP. The Battle Tower unlocks after you’ve defeated all eight of the Gym Leaders, and you want to test your skills against some of the harder portions of the game.