The bank is Millibelle, a friendly banker who guards your Geo, then runs off with it the moment you save up enough.
The bank in Hollow Knight is run by Millibelle the Banker. Per the wiki, she sets up a stand at the base of 
Fog Canyon and offers to keep your Geo safe so you do not lose it when you die.
According to the wiki, it sounds like a fair deal. Geo in her vault survives death and can be pulled out whenever you want. The catch, which the game never warns you about, is that Millibelle is a thief.
Once your balance climbs high enough, she packs up and vanishes with your savings. This guide covers how the bank works, the exact amount that triggers the theft, and how to track her down and take back more 
Geo than she stole.
Millibelle the Banker, at the base of Fog Canyon. 100 Geo to open an account, then deposits are safe from death up to 4,500.
Hold 2,550 or more and rest at a bench or take a Stag, and she runs off.
Find her at the Hot Spring and bounce her with the Nail for about 1.5x back.Per the wiki, Millibelle keeps her bank at the base of Fog Canyon, the floaty acid-and-jellyfish region west of the 
City of Tears. Her stand sits in a small room near the bottom of the area.
According to the wiki, you reach her on the normal route through Fog Canyon, the same path that leads toward 
Quirrel and the Teacher's Archives. There is no puzzle to open the bank, she simply calls you over the moment you pass.
Pick up a Fog Canyon map from Cornifer before exploring. The acid pools and tight jellyfish rooms are far easier to navigate once the bank room is marked on your map.
Per the wiki, opening an account costs a one-time fee of 100 Geo. After that you can deposit Geo in any amount and withdraw it at any time.
According to the wiki, banked Geo is kept safe when you die. Normally death drops your Geo as a Shade you have to fight back to, so the bank looks like a clean way to protect a big balance.
| Detail | Value |
|---|---|
| Account fee | 100 Geo, one time |
| Maximum balance | 4,500 Geo |
 Kept on death | Yes, the vault is safe from your Shade |
| Theft trigger | Holding 2,550 or more, then resting or using a Stag |
The wiki notes that the vault caps at 4,500 Geo, so it cannot hold an unlimited fortune. In practice, that cap matters less than the hidden theft rule, which most players hit long before reaching it.
Per the wiki, the trap springs once Millibelle is holding 2,550 Geo or more. The next time you rest at a bench or travel using the 
Stagways, she abandons her stand.
According to the wiki, returning to the bank afterward shows an empty booth. Striking the empty stand three times reveals it was only a 2D cutout, and the bank sign drops to the floor as you leave. Millibelle is long gone with your savings.
The wiki states that she resurfaces as Millibelle the Thief at the Hot Spring inside the 
Pleasure House in the City of Tears. In real runs, this is the moment most players realize the bank was never safe.
Per the wiki, you can take your money back, and then some. Head to the Hot Spring in the Pleasure House, where Millibelle the Thief is relaxing in the water.
According to the wiki, hitting her with your 
Nail bounces her around harmlessly and showers Geo out of her. The amount you can reclaim is roughly the Geo you deposited times 1.5, for a maximum of about 6,834 Geo.
Because the payout is about 1.5x your deposit, the bank can actually turn a profit if you deposit a large sum on purpose, trigger the theft, then farm her at the Hot Spring.
Per the wiki, the honest banking service is a trap, since any large balance will eventually be stolen. If you only want safe storage, the bank is not reliable.
According to the wiki, the smart play is to treat the theft as a feature. Deposit a big sum, trigger the getaway, then claim the 1.5x payout. Pairing it with a 
Geo-boosting charm while farming makes the whole detour pay off.
The wiki notes that you are never forced to use the bank to finish the game. In practice, it is best seen as an optional side story with a cash reward rather than a true savings account.
The bank ties into the Geo you earn, the maps that chart Fog Canyon, and the other vendors who want your coins. These spokes pick up the connected threads.
Game data and screenshots adapted from hollowknight.fandom.com, used under CC BY-SA 3.0. Original content remains the property of the wiki contributors and Team Cherry.