Intensity

Ok, so intensity. Self-explanatory, how hard things are...

The formula for rewards: F-rank * Intensity Intensity:

1: Virtually no enemies

2: Some enemies, but they are HORRIBLE

3: More enemies who are bad

4: Below average enemies

5: Average enemies

6: Formidable enemies

7: Strong enemies and Trent

8: Demonic enemies

9: VERY HARD

9.9: Limit, solo clear certain levels to advance

10: Dominant-rank opponents

10.31: Halloween Spirit, oh no

11.26: Turkey God, prepared to die of bird loss

12.24: Spirit of Christmas Past: Resets time occasionally, if you're being naughty

12.25: Spirit of Christmas Present: Deprives you of joy by doing what you hate most

12.26: Spirit of Christmas Future: Occasionally inflicts "Bloodlust" and "Fear" effects on people, might instantly kill

13.1: New Year's, safe zone, but can only be reached by killing all three Spirits listed above

19.4: Independence Day: Aliens will come and inflict major damage, The Purge will happen until you transcend the level.

23.11: Veteran's Day, all veterans from Obese Seal Training (Str * 1000) will relentlessly attack you with Bloodlust (2) effect on them.

After that, there is just more pain and Trent will attack you more often. I will be very surprised if you go 23.11 solo without death.