if you are talking about Claire go to black thorn if you are talking about blue then you need to beat every gym if your talking about blues floor puzzle cant help ya
The last gym is in viridian city
in mohgaony town
Blue, the last gym leader in kanto region
Blackthorn if you are including Kanto its Viridian Pokegamer01
beat the last gym leader on soul silver in johto
the 15th gym leader in soul sliver is blaine and he uses only fire type pokemon
you have to use surf through passage ways
try the improved elite four or try to beat red on mount silver.
you battle them in the dance center after you defeat Claire, the last gym leader in johto
The Kanto gym leaders come in no particular order, but Blaine is typically the last gym leader fought, and also the second to last gym leader appearing on the Trainer Card.
Ghost Pokemon.
DRagons den you going fight vs the last gym leader from hoenn and the last from the elite four ( they are hard )