Grotto

The grotto is located at the bottom of your main base, and provides a way for you to get rid of hopefully unwanted things from your inventory and receive some random things in return. The grotto costs 2500 steel, 2500 fuel, 2500 recruits, 25 resonators, 25 flywheels, and 2h to open. There are no further upgrades (like some buildings, it starts at level 1 in the destroyed state, and rebuilding it returns it to level 2).

Once you've opened the grotto, you can go inside to trade with the ship captain. The ship captain will have a set of 25 things that he is requesting. Usually these are research items, resources, troops (basic or base versions of weaker "premium" ones) or producable supports; sometimes resonators or flywheels will also be in the list of requests. You can pick any items that you want in the grid (their position doesn't matter for the purpose of request fulfillment count or order, but towards the bottom requests tend to increase in number of resources or items requested) to give to the captain, and for every 5 requests that you fulfill, you will get a higher-tier cargo. Choose the items that you want to trade, and once you've contributed everything that you want to contribute, click the "Send" button. The ship will be gone for 1 hour, and then return with your cargo. Then the cargo has to be unloaded, which takes 1 hour per level. Once this is done, you can finally claim the contents.

In general, it's not worth it to do all 25 since some of the requests in the grid are usually quite expensive; of course, the best strategy depends on what you have the most of and that is least useful (for example, it's probably better to give 15 level 1 research items than 1 level 4 research item) and on which items you wish to obtain.

 25 | V (Legendary) | 5h

The cargo contents (like chests) are fairly random, so sometimes you'll get something useful and sometimes you won't. (You can get some items, such as Ardheim components, that you don't get in normal chests, however.) Because of the randomness, most people don't consider the grotto very worthwhile; see Commentary:Grotto. MacDrum's guide also has some advice.

As of November 22, the Grotto has been revamped in an attempt to make the rewards generally more worthwhile. The changes include:

* Rewards will always include some flywheels, resonators, keys, or city plans.
* Rewards will always include equipment blueprints and crafting materials, with rarity equal to the rarity of the cargo obtained.
* Rewards will include Ardheim items with similar rarity.
* The probability of getting equipment or repair kits has been increased.

The full rewards table is as follows. You will always receive exactly one entry (which might be nothing) from each line in the table.

* 1-4 Drawing (13%), 1-2 Set of drawings (12%), 1-4 Flask with genetic material (13%), 1-2 Syringe with genetic material (12%), 1-4 Faceted ionite (12%), 1-2 Ion insulator (12%), 1-4 Occult rune (12%), 1-2 Occult medallion (12%)
* 1-2 City plans (20%), 1-2 Flywheel (20%), 1-2 Resonator (20%), 1-3 Key (40%)
* 1 BRK Mk.I (10%), 1 MRK Mk.I (14%), 1-2 SRK Mk.I (19%), 1-3 Spare parts (40%), nothing (17%)
* 1 Industrial paint (25%), 1 Wooden beam (25%), 1 Duct tape (25%), 1 Nails (25%)
* 1 Leather belt (12%), 1 Clip (11%), 1 Spring (11%), 1 Lens unit (10%), 1 Kevlar fabric (10%), 1 Powder charge (9%), 1 Rifled barrel (9%), 1 Individual bandages package (9%), 1 Wooden stock (9%), 1 Steel plate (9%)
* 1 Blueprint for Infantry pistol M14 (25%), 1 Blueprint for protective glasses (25%), 1 Blueprint for first aid kit (25%), 1 Blueprint for guardsman durable coat (25%)
 Rare | * 200-250 Steel (20%), 200-250 Fuel (20%), 200-250 Ionites (20%), 200-250 Ammunition (20%), 200-250 Recruits (20%)
* 1-2 Folder with drawings (13%), 1-2 Set of drawings (12%), 1-2 Occult seal (13%), 1-2 Occult sphere (12%), 1-2 Ampoule with genetic material (12%), 1-2 Capsule with genetic material (12%), 1-2 Ion indicator (12%), 1-2 Ionite battery (12%)
* 1-3 Key (25%), 1-2 City plans (25%), 1-2 Resonator (25%), 1-2 Flywheel (25%)
* 1-2 BRK Mk.II (10%), 1-2 MRK Mk.II (12%), 1-2 SRK Mk.II (12%), 3-6 Spare parts (47%), nothing (20%)
* 1 Wrench (14%), 1 High voltage wires (15%), 1 Techplate (14%), 1 Industrial paint (14%), 1 Wooden beam (14%), 1 Duct tape (14%), 1 Nails (14%)
* 1 Armored shoulder pad (11%), 1 Silencer (12%), 1 Thunderflash (11%), 1 Helmet skeleton (11%), 1 Analgesic (11%), 1 Four-edged bayonet (11%), 1 Drum (11%), 1 Weapon bipod (11%), 1 Threaded file (11%)
* 1 Blueprint for "Shorty" revolver (25%), 1 Blueprint for engineer's regiment forage cap (25%), 1 Blueprint for cartridge belt (25%), 1 Blueprint for mercenary coat (25%)
 Special | * 350-500 Steel (20%), 350-500 Fuel (20%), 350-500 Ionites (20%), 350-500 Ammunition (20%), 350-500 Recruits (20%)
* 1-2 Folder with drawings (13%), 1-2 Set of drawings (12%), 1-2 Occult seal (13%), 1-2 Occult sphere (12%), 1-2 Ampoule with genetic material (12%), 1-2 Capsule with genetic material (12%), 1-2 Ion indicator (12%), 1-2 Ionite battery (12%)
* 1-5 Flywheel (25%), 1-5 Resonator (25%), 3-5 City plans (25%), 3-5 Key (25%)
* 1-2 BRK Mk.III (10%), 1-2 MRK Mk.III (12%), 1-2 SRK Mk.III (12%), 4-8 Spare parts (47%), nothing (20%)
* 1 Block of cylinders (20%), 1 Radiator (20%), 1 Wrench (20%), 1 High voltage wires (20%), 1 Techplate (20%)
* 1 Vambrace (13%), 1 Air filter (12%), 1 Boot with heels (13%), 1 Box magazine (12%), 1 Set of gears (12%), 1 Adjustable Key (12%), 1 Handguard (12%), 1 Tactical belts (12%)
* 1 Blueprint for AG-8 assault rifle (25%), 1 Blueprint for Liquidator tactical visor (25%), 1 Blueprint for anti-tank grenade (25%), 1 Blueprint for "Storm" MK. II Battle armor (25%)
 Elite | * 500-750 Steel (20%), 500-750 Fuel (20%), 500-750 Ionites (20%), 500-750 Ammunition (20%), 500-750 Recruits (20%)
* 1-2 Set of drawings (13%), 1-2 Complete set of drawings (12%), 1-2 Occult sphere (13%), 1-2 Occult obelisk (12%), 1-2 Capsule with genetic material (12%), 1-2 Retort with genetic material (12%), 1-2 Ionite battery (12%), 1-2 Ionic drive (12%)
* 3-6 Flywheel (25%), 3-6 Resonator (25%), 5-7 City plans (25%), 5-7 Key (25%)
* 1-2 BRK Mk.IV (10%), 1-2 MRK Mk.IV (12%), 1-2 SRK Mk.IV (12%), 8-10 Spare parts (47%), nothing (20%)
* 1 Generator (20%), 1 Transmission (20%), 1 Stator (20%), 1 Block of cylinders (20%), 1 Radiator (20%)
* 1 Disc shop (10%), 1 Bolt action (10%), 1 Tactical gloves (10%), 1 Stimulant (10%), 1 Firearm receiver (10%), 1 Folding stock (10%), 1 Set of tools (10%), 1 Filter of heighten productivity (10%), 1 Aiming lens (10%), 1 Ebonite armor plates (10%)
* 1 Blueprint for Heavy machine gun "Stormhardt" (25%), 1 Blueprint for Lord-costable helm (25%), 1 Blueprint for gun repair kit (25%), 1 Blueprint for "Shadow" light armor (25%)
 Legendary | * 750-1000 Steel (20%), 750-1000 Fuel (20%), 750-1000 Ionites (20%), 750-1000 Ammunition (20%), 750-1000 Recruits (20%)
* 1-2 Complete set of drawings (13%), 1-2 Two-volume drawings (12%), 1-2 Occult obelisk (13%), 1-2 Violated token (12%), 1-2 Retort with genetic material (12%), 1-2 Barrel with genetic material (12%), 1-2 Ionic drive (12%), 1-2 Ionite generator (12%)
* 5-7 Flywheel (25%), 5-7 Resonator (25%), 5-8 City plans (25%), 5-8 Key (25%)
* 1 BRK Mk.V (10%), 1 MRK Mk.V (12%), 1 SRK Mk.V (12%), 8-12 Spare parts (47%), nothing (20%)
* 1 Generator (33%), 1 Transmission (33%), 1 Stator (33%)
* 1 Callibrated trigger (13%), 1 Ebonite tube (12%), 1 Composite steel (13%), 1 Ionite powerslot (12%), 1 Flash suppressor SK-19 (12%), 1 Receiver (12%), 1 Armored breastplate (12%), 1 Reinforced duct tape (12%)
* 1 Blueprint for Gideon's sniper rifle (25%), 1 Blueprint for "Iron veteran" mask (25%), 1 Blueprint for high-precision scope (25%), 1 Blueprint for "Tesla" armor (25%)
* 1 Gideon's sniper rifle (3%), 1 "Iron veteran" mask (3%), 1 High-precision optical sight (3%), 1 "Tesla" armor (3%), nothing (89%)
* 1 Encrypted Data: Constable Preston (2%), 1 Wanted: Tarrus Valentine (2%), 1 Dominion Figher tag (3%), 1 "Magic of Tesla Energy" Book (3%), 1 Kill Lists (3%), 1 Artillerty Regiment Patch (4%), 1 Turret Blueprint (4%), 1 Patient file (5%), 1 Title-document (4%), 1 Flamethrower Recipes (5%), 1 Piece of Mutagen Formula (5%), 1 Sacred Code of Emper (5%), 1 Explosive Cannon Ball (5%), 1 Case file: Phantom Ranger (5%), 1 Digest of Tactical Doctrines (5%), 1 Iron Empire Medal (5%), nothing (35%)

Your journal has this to say about your grotto:
*After the Renascent Steel Empire had been created and the Osterberg fortress had been captured, the "Iron Armada" trading ship contacted with Commander Grant. According to the eyewitnesses, the Resistance leader was really surprised. It seemed like merchants from "Vendor" didn't care whether to deal with the Dominion commander or the elderly commander of the Iron Empire.*

*Merchants asked about a grotto closed to the public. They asked the "crimson ones" to clear the caves and allow them to leave a person in the fortress, so that they could communicate with the local garrison and coordinate subsequent visits and supplies.*

*The predecessor of Commander Grant didn't approve it, because there weren't enough people to even protect the fortress, not to mention the construction work to improve it.*

*Grant is a far-sighted person, so he ordered Captain Walker to select people to "unseal" the Grotto, despite the deplorable state of the fortress defense. The Osterberg gates are still open because of the last assault.*

*-- Choose up to the ten real trustworthy fighters and order them to keep an eye on that "Vendor" representative. I'm not going to disregard supplies. Due to the constant war, we won't face with the shortage of tokens, but I don't want spies and instigators to be here. -- ordered the leader of the resistance to captain Walker. -- And if he gives even the slightest reason for suspicion, the "Vendor" will go down with all the traders on board. No compromise.*