Starting at floor 601 and rushing is the fastest way to cap your Resistance Power (RP).
"Haste/Increased Priority" skills are essential to counter high-AGI enemies in higher floors. 3. Key Superbosses and Encounters Labyrinth of Chaos/Tips - Monster Girl Quest - Miraheze Labyrinth of Chaos
Complete the main story and access the bookcase in Hades. Starting at floor 601 and rushing is the