Erix and Rin cleared up to the 24th Floor.
The 25th Floor's requirement was 200,000 Power Level. Even though they could try and use a chance, they decided to end floor clearing for now.
From the 21st Floor to the 24th Floor, they got 4 Advanced high-grade elemental crystals.
Erix could use those crystals to progress in the only Advanced element affinity he had—Metal.
Meanwhile, Rin had two advanced element affinities—Lightning and Blood. She had already decided to prioritize Lightning.
Since these were 'High-grade' elemental crystals, they could be helpful until one reached the 7th realm in elemental affinities.
Low-grade elemental crystals could help progress up to 3rd realm.
Medium-grade elemental crystals could help progress up to the 5th realm.
High-grade elemental crystals could help progress up to the 7th realm.
Finally, Peak-grade elemental crystals could help progress up to the 10th realm.