Quote Originally Posted by nik0tine
The key to this place is to have Quistis at critically low hp and the blue magic degenerator. She can kill any monster there in one hit with that spell. (It helps to have her equiped with initiative)
Exactly. What's particularly notable about Degenerator is that it is remains fully effective regardless of Quistis' statistics or level. Since level is irrelevant, Degenerator allows one to level up rapidly. The significance of this can be seen here.

Quote Originally Posted by masamune1600
Degenerator, as suggested, is a common Island Closest to Hell strategy. Since every monster is at Level 100 regardless of the characters' levels, one can level up very quickly from a low level. Thus, by using the GF abilities that give bonuses to stats at level ups, one can add massive bonuses to the overall statistic. Degenerator is important because it always works on these monsters, destroying the target regardless of HP (obviously an issue when one starts at low levels). That is the generally accepted strategy for this method of stat-raising.