The Pile Driver (パイルドライバー) is a device used to purify Immortals, which is set up by Otenko in an appropriate spot with enough space. Immortals can be purified only with the Pile Driver, which incinerates their source, the dark matter, and prevents them from reviving. After defeating an Immortal, Django has to drag him in a coffin and place him in the center of the Pile Driver, then activate the Generators around it. The Generators have been blessed by "Gaea," the Motherland, and "Sol," the Sun's spirit, and can amplify solar energy. The Pile Driver can't be activated without sunlight, and will be more powerful the more sunlight is hitting the solar sensor. The Immortal will try to resist by using Ectoplasm to attack Django. In Boktai 2 and 3, the Immortal can move and can deactivate the Generators, and tries to escape if all four are inactive, so Django has to push him back to the coffin until he's purified.
In Boktai 2, Sabata uses the Pile Driver to save Django, who was bitten by a vampire, and is wounded because of his dark powers. When Django tries to purify Red Durathror while in his vampire state, he almost dies, but with the help of the townspeople he manages to survive and returns to normal.
The Piledriver system in Lunar Knights is entirely different from the Piledriver in the Boktai games. First, it is not the large circular array imprinted on the ground it used to be. It is now a giant satelite in space that absorbs its energy from the sun. It is operated by the new sunflower girl, Alice. Second, it is a LONG way to the Piledriver. The player - controlling Lucian and Aaron aboard the mobile fighter Laplace - must fight their way through space, defeating fleets of ships while keeping up energy and life, until they meet the boss at the end. This is usually Perrault. When Perrault is defeated, Laplace will send the coffin to the Piledriver. There will then be a cutscene showing the immortal being purified, and then the player earns 1 (or 2) terrenials; the player does not actively take part in the purifying process beyond traveling to the Piledriver. The piledriver itself, simply named Sunflower in the English release, works with the use of numerous satelites and mirror panels. The panels absorb solar energy from the sun and use it to purify the vampire in the coffin. This is the only possible way to purify a vampire since the paraSOL was implemented. Also, this Piledriver acts as the docking bay for Laplace when it is not in use (though it also docks with it when a Vampire is ready for purification). As with the other games, there is a final variation to the Piledriver system. This is against the immortal Polidori. The player strikes Polidori with Laplace's cannons and eventually, Laplace goes inside the body of the enlarged Polidori. Laplace destroys his insides and it is believed that Polidori is defeated and purified. Though it seems to have nothing in common with the Piledriver of the past, there is one connection; this Piledriver generates a circular array (presumably composed of solar energy) to suspend the coffin in space, which is very similar to(if not the same) the array of the old Piledriver.