Geo

Description
''The currency of Hallownest, made from fossilised shells of various forms. Can be traded for goods or used as toll in various old mechanisms.''

There are three types of Geo drops:

Use
Used to buy goods from merchants or to pay tolls for Stag Stations and Benches. Also used to pay the Nailsmith to upgrade The Knight's Nail.

Tolls

 * for Stag Station
 * for all Bench Tolls

Merchants

 * for all of the maps from Cornifer ( if bought from Iselda)
 * for Iselda's stock (charms and pins)
 * for all three Fragile Charms bought from Leg Eater ( if wearing Defender's Crest)
 * to unlock all of the trials at the Colosseum
 * to make a bank account with Millibelle ( for a return of an extra )
 * to fully upgrade the Nail
 * to buy everything from Salubra ( for the Charms + for Notches +  for her Blessing)
 * to buy everything from Sly
 * to upgrade all Fragile Charms to Unbreakable at Divine
 * per Rancid Egg bought from Tuk (infinite supply) (Not available on Steel Soul Mode)

Miscellaneous

 * to learn Dash Slash from Nailmaster Oro
 * to be thrown into the fountain found in Ancient Basin for a Vessel Fragment

Summary of Costs

 * to buy everything at the most sparing prices
 * to buy everything without extra exertion ( difference)

How to Acquire
Geo can be gained in several different ways:


 * Defeating enemies
 * Destroying Geo deposits
 * Opening chests
 * Selling relics to Relic Seeker Lemm
 * Rescuing Grubs for the Grubfather
 * Completing a Trial at the Colosseum of Fools

While the Gathering Swarm Charm is equipped, a small swarm will gather any dropped Geo for the player, except those fallen in water or acid. Fragile Greed (as well as it's unbreakable variant) increases the amount of Geo enemies drop.

Keeping Relics to sell to Lemm when Geo is needed is particularly useful because unlike Geo, these items are not lost upon death.

In Steel Soul mode, Rancid Eggs can be sold to Steel Soul Jinn for Geo.

A great early source of Geo are the Husk Guards in Forgotten Crossroads. Many enemies in the City of Tears, especially Great Husk Sentries, as well as Hoppers and Great Hopper in Kingdom's Edge, are also great sources of Geo.

The fastest ways to farm Geo later in the game are to continuously complete the Trial of the Conqueror, or to farm Dirtcarvers and Carver Hatchers in the Failed Tramway with Fragile Greed or Unbreakable Greed equipped.

One-time Major Sources

 * Gorgeous Husk in the City of Tears drops upon death ( with Fragile Greed equipped)
 * In Kingdom's Edge, there is a hidden passage accessible by breaking a wall in a room with a Great Hopper and a lot of spike pits. At the very bottom of it is largest Geo deposit in the game, rewarding . This value is not increased by Fragile Greed.
 * Millibelle the Thief will return when in the Pleasure House. See here for more details on this process.

Geo Geo Гео Geo