Floor 21 is the 21st floor of Infernal Tower.
- Infinite Cerberus Kids spawn after 0 seconds0f, delay 2~6 seconds60f~180f.
- 10 B.B.Bunnies spawn after 3.33 seconds100f, delay 1.33~3.33 seconds40f~100f.
- 2 Shy Boys spawn after 13.33 seconds400f, delay 3.33~6.67 seconds100f~200f.
- 1 St. Pigge the 2nd spawns after 10 seconds300f.
- When the base reaches 99% HP:
The return of everyone's favorite floor, now made even worse than it already was! The startoff is similar to the original one, but Those Guys have been replaced by Cerberus Kids, St. Pigge the 2nd is twice as strong, and the stage length has been made shorter. And for the boss wave, AVOID LURING AT ALL COSTS! The Hackey will obliterate your base in usually just 2 hits, and without any cats with Slow or Knockback, time will already be very tight before you defeat the Red Cyclone. It may be a good idea to not bring Backliners as they'll likely die to the Hackey, instead bring pretty much as many Anti Reds and maybe some Anti Floatings like Fishman and Cameraman for the Cyclone.