When the lighter was relit, Polpo's Stand, Shadow Sabbath, appeared and attacked. Giorno is able to see through Shadow Sabbath's weakness and faces it alongside Koichi. Koichi realizes that the arrow is involved in this situation and they realize that the point of Polpo's exam is to try to create more Stand users.
And that must be the motive 
behind Polpo's test!
ولا بدّ وأنّ هذا هو الدّافِع وراء
!اختبارا بولبو
Und das war wahrscheinlich auch
der Hintergedanke bei Polpos Test.
Ese debe ser el verdadero motivo
tras la prueba de Polpo.
Ese debe de ser el verdadero motivo
tras la prueba de Polpo.
Et l’épreuve de Polpo vise sûrement
à créer des détenteurs !
Dev'essere quello il motivo
del test di Polpo!
Deve ser esse o objetivo
do teste do Polpo!
Наверняка, в этом и есть 
смысл испытания Польпо!