The Life Orb is a held item that drains the life of the Pokémon that holds it. It may sound bad, but it gives the advantage of increasing the Pokémon's attack power. Whenever the Pokémon scores a hit, the Sphere of Life steals some health. The health taken is not a huge amount, which makes this article great. This is where you can find the Sphere of Life in Pokémon Brilliant Diamond and Brilliant Pearl.
To get to the Life Orb, you first need to get to Stark Mountain. To reach this area, you'll first need to defeat the Elite Four and get the National Pokédex. After both objectives are completed, go to Snowpoint City and take the boat to the combat area. Head north on Route 225 to the Survival Area. From here, head east until you reach Route 227. You will know this is the right area because the ash will fall from the sky.
Head north and stop at the house along the way if your Pokémon need treatment. Take the stairs near the house and ride your bike along the platform on the other side. Head north through tall grass and jump over a few barriers to reach the trainer on the right hand side. After defeating him, head north until you reach the stairs.
Instead of taking the stairs, use Rock Climb on the cliff on the left. This will take you to a trainer. Defeat him and use Rock Climb on the cliff behind him. Go left when you reach the bottom of the cliff to find another area where you can use Rock Climb. Grab the rocks and you will land next to an object. Collect it to get the Life Orb.