Pokémon Diamond and Pearl/Turnback Cave

Turnback Cave is a dungeon that opens with the Spring Path when you get the National Pokedex. Inside are high level Pokémon. Also, you cannot use an Escape Rope to get out. Before proceeding, use Defog to clear up everything and make looking around and battling much easier.

Giratina
Giratina randomises this cave's space and time. To get to it, you are supposed to enter three rooms each having a pillar in the middle, before going through total 30 rooms, excluding the entrance room. The key is to find an out-of-place rock in the formations, and go to a door near or opposite it. You will also need to use the Rock Smash move at times. Wild Pokémon increase in level every time you pass a pillar. However, in the entrance and rooms with a pillar, no wild Pokémon appear. If you exit any door by which you just entered, or fail to press A on three different pillars, you will be back at the entrance; then press A on the slab there to restart the 30 rooms countdown. After seeing the third pillar, go through any door (except the entry) and you will be in the final chamber. Which has no wild Pokémon other than a waiting Giratina.

Battling
Giratina is an extremely strong legendary Pokémon. Right now, the four moves it knows make the battle pretty easy. Here's how to capture it:


 * First reduce most of its HP. Use Ghost, Dragon, Dark or Ice type moves to weaken it, but make sure you don't KO it.
 * Status ailments such as PAR, FRZ and SLP are also a good idea (do not burn, poison or confuse as this may KO Giratina before you have a chance to capture it).
 * Use moves such as Charm, Screech and Scary Face, or use Pokémon with abilities such as intimidate to sharply lower Giratina's stats. This will help make catching the Pokémon easier.
 * Giratina vanishes one move before using Shadow Force. Switch to a Normal type Pokémon to avoid getting damage (immune to Ghost type moves). Once it has used Shadow Force five times, you may want to use a Ghost/Flying type Pokémon or a Ghost type that knows the ability Levitate. This will eliminate any chance of receiving damage from Slash and Earth Power.
 * Start throwing Poké Balls once you feel you have lowered its stats and HP enough.

After battling
Note that whenever you come back after catching/defeating Giratina, after coming to the room where it once stood will get you an item, either a Reaper Cloth, a Rare Bone, or a Stardust (depending on how quickly you reach the room). The inscription in the entrance of the cave also changes after your battle with Giratina.