First go to Sendoff spring and get trough the tall grass {it may be possible that you can't escape form wild pokemon} now you will see a cave enter it the turnback cave can fool you every time so keep on the same path.keep on the keep going to the right door {in some cases you must use other doors} if you are in a room with blue air you will see Giratina.Press A and he will cry and battle against you.Try to capture him but it will take a long battle.if you manage to capture him a portal to the disortion world will appear.

get into it you will only see a part of the area search around until you found a pokeball.

get it and you recieve an item called girseous orb it can make Giratina's form change if you give him the orb!

Note:Giratina's evolution shall not be put into the Sinnoh Pokedex or national Pokedex.