Bosses
Underfell EXP fight around level 4000.
Bob: Underfell EXP fight around level 4000. Get it by Back middle of Underfell. Use it to Stop when Hyper Dust Sans or Rudinn is faster for your level.
Underfell fight. The EXP route disagrees with itself on whether Bob is used until 4250 or 4900.
| Fact | Value |
|---|---|
| Name | Bob |
| Location | Middle of Underfell |
Back middle of Underfell.
Stop when Hyper Dust Sans or Rudinn is faster for your level.
The Roblox games record, updated October 29, 2026, lists game version 12.4. The description says the experience is based on Undertale by Toby, names creator YaoYN, and links the YN Studio group. That record does not include an itemized patch note.
Two public descriptions disagree. A game reference says the barrier's final room accepts a reset at level 6000 with 70 TP, then wipes level and TP and applies a level booster that can stack to 34 percent. A November 2026 walkthrough instead says level 6000, 100 TP, and a gold fee, and that weapons stay. Check the barrier prompt on your save before you spend the run.
Open Menu at the top right, then Settings, type the code into the box labeled Code here, and press Redeem code. Current code lists say the account must be in the YN Studio group. Codes are reported as case sensitive and single-use per account.
Community guides say you need level 6000, then spend 100 Kromer per spin at Ralsei's Skill Awakening Workshop in Castle Town. Upgrading a skill you already have is described as another 200 Kromer. The Extra capacity pass adds 18 skill-storage slots.