Like most things in Borderlands 3 (such as your multiple weapon and class mod slots), the Artifact slot in your inventory menu is unlocked naturally by playing through the story campaign.

Borderlands 3 is officially here, and one of its more interesting new mechanics is something called the Lost Loot Machine. At long last, players don’t necessarily need to make a tough decision when they encounter a nice piece of loot but don’t have any room for it in their inventories. The Lost Loot Machine will pick up loot that was left behind and allow you to access it later, but there are some things to keep in mind before you begin relying on it.

First thing’s first: the Lost Loot Machine won’t pick up every piece of loot you leave behind. It will only collect items of higher rarity – that means items that are blue, purple, or orange. Those white and green drops will be left behind by the Lost Loot Machine, as Gearbox says it will never collect items of those rarities.

Another thing to consider is the fact that the Lost Loot Machine will ignore items you drop yourself, regardless of rarity. Loot that you drop from your inventory is considered “discarded” by the Lost Loot Machine, so it will pass those up in favor of loot dropped by enemies.

Just like your character’s inventory, the Lost Loot Machine has a limit on how many items it can pick up as well. That means you can’t walk around with a full inventory the entire game and let the machine do the heavy lifting, as it only has a finite amount of storage space. You can upgrade its storage by purchasing Storage Deck Upgrades from Marcus Munitions on Sanctuary, but you’ll need to clean it out periodically to make sure it has space for more loot.

Finally, the Lost Loot Machine won’t pick up anything while playing multiplayer in Coopetition mode, but it will function normally while playing in Cooperation mode. The Lost Loot Machine is indeed one of the most exciting additions to Borderlands 3, so keeping these rules in mind will help you take full advantage of it.

Story Timeline

There's a lot to take in and discover when playing Borderlands 3, and even returning fans may not realize several key elements to the game that aren't explicitly told to you. We've rounded up several noteworthy mechanics and elements to Borderlands 3 that the game doesn't outright tell you, which you can view below.
Other Borderlands 3 Guides:

• Borderlands 3 Shift Codes!
• Easter Eggs and References.
• How to Respec Your Character and Costs Explained.

Some Useful Tips and Tricks

How to Unlock Weapon and Item Slots
When you start Borderlands 3, you'll only be able to swap between two equipped weapons, and will only have access to a grenade and shield - so when does everything else unlock? Over the course of the game you'll eventually get two more weapon slots, as well as Class Mods and Artifacts to equip as well. Depending on how fast your moving through areas, you may even start finding items you cant even equip yet.
These unlocks are tied to completing story quests, so here's when you can expect to unlock them.

• Your Third Weapon Slot will unlock after leaving Pandora for the first time, completing the Taking Flight and Sanctuary quests at are your 4th and 5th main missions.
• Your Class Mod Slot will unlock after helping Rhys out on Promethea and defeating the boss and completing the quest Hostile Takeover, which is your 6th main mission.
• Your Fourth Weapon Slot will unlock after completing the first vault mission in the main story, Beneath the Meridian, which is the 10th main mission.
• Finally, your slot for Artifacts will only unlock after taking on another Vault quest called Cold as the Grave, which is the 16th main mission.

Regions are (Mostly) Level-Locked
As you journey across the stars in Borderlands, you'll find out pretty early on that enemies will stick a certain level range when entering new areas and taking on missions. This means that - for the most part - if you pass on a side mission and go back later, you'll likely find both the difficulty and rewards well below your level.
Similarly, if you dash on ahead through main missions as fast as you can, you may start encountering enemies well above your own level, and all the loot they drop may also be unavailable to equip until you can catch up, which can really suck!
Because of this, it's worth your while to stop and smell the flowers - and by that we mean take on side missions, scope out challenges, and generally explore and do whatever you can before moving onto the next area. Certain side missions will appear in areas before or after completing a main mission in that area, so be sure to look around and make sure you don't miss anything.
However, once you reach certain story beats that may return you to past areas, and when you beat the game, enemies in older zones will sometimes increase in difficulty to a certain point. Beyond this, enabling Mayhem Mode once you beat the game will automatically bring all enemies up to level 50 to increase threat and rewards.
Loot the Best Chests ASAP (Or Wait for Mayhem)
These chests will either have the best loot, or the worst loot depending on when you find them.

Borderlands 3 Class Mods Wiki

With regards to level-locked regions, it's very important to note that both Red Chests (usually found after bosses or as bonus unlocked areas from side missions) as well as Typhon Dead Drops (crew challenges triangulated from finding recordings) are also locked to the region of that area (unless a region eventually upgrades over the course of the story).
For that reason you should always be exploring and looting chests in every region as you progress - as saving them for later will only lower the value of what's inside 5 levels later.
However, Mayhem Mode changes this, as it will bring all the chests up to your level along with all other loot and enemies in the region. With Red Chests, you can re-open them each time you quit the game and start anew, while Typhon Dead Drops can only be looted once - so make sure you think hard about when you want to open these. If you miss your chance to get the best loot for your level, come back once you've beaten the game to unlock the other dead drops with Mayhem Mode enabled.
Class Mods Can Boost Locked Skills
Fake it 'til you make it.
Once you start finding Class Mods on Promethea and beyond, you'll notice that they will grant extra points in each of your three skill trees. The better the quality, the more skill points they'll add to more skills.
It's worth noting two things: A Class Mod can further enhance a skill that you've already maxed on the skill tree, which means you can boost the rate of damage or cooldowns and such beyond normal levels.
Secondly, even if you haven't unlocked a skill yet, you don't need to have a point in a skill for a Class Mod to give you that skills effects! Knowing this, you can essentially look for Class Mods to bolster skills in a tree you aren't focusing on to give you an edge in multiple areas at once.
Where Are The Challenges?
Challenge Unlocked - You Found the Challenge Tab
The menus of Borderlands can be.... difficult to navigate at times. Guardian Ranks have their own slot in your ECHO menu, and you can't even check them out until you beat the game. They also take the place of where Challenges were in Borderlands 2 - but that doesn't mean they are gone.
You may start noticing as you play that you'll get notifications that challenges have been met, but they don't appear to be tracked anywhere. If you look at your map, the Challenges Tab only tracks 'Crew Challenges' which are side objectives to uncover in each area.
As it happens, the regular Challenges are hiding deep in the map menu. Hit the Orbit View until you are in the galaxy view of the map, and then click on the Challenges tab. Instead of Crew Challenges, you'll finally see the Challenges you can unlock for killing certain types of enemies, with different weapons, or looting certain items.
Unlike Borderlands 2, Challenges in this game do not unlock bonus stats. Instead, you'll get extra Eridium for each challenge met. Rank 1 will award 1 Eridium, Rank 2 will give 2, and so on until the challenge ranks are all met. Be sure to check your Challenges from time to time to unlock more Eridium, and use it to unlock exclusive rewards from Earl aboard the Sanctuary.
When Can You Mine Eridium?

These purple rocks can be easy to miss.
As you explore Pandora an other planets, you'll likely come across purple rocky mounds that look suspicously like Eridium - but hitting them with your melee attacks proves fruitless, at least for now.
It won't be until much later in the game - you need to complete the 10th Mission: Beneath the Meridian - that you gain the ability to harvest Eridium Ore from the ground wherever you may find it, which can be extremely useful for amassing an Eridium horde. All you need to do once the upgrade is obtained is smash the purple rocks with melee attacks.
Aside from that, your best ways of finding more Eridium are killing (obviously), and taking a spin on the Slot Machines for small Edirium payouts. You can then use the Eridium to either take your chances on the Vault Line Slot Machine, or go see Earl at the bottom of the Sanctuary spaceship to buy special cosmetics and weapons in exchange for the currency.
Respec to Become a New You
Respecing your Skill Tree is easy when you're broke!
Once you've gotten at least one skill point, and decide that skill you've invested in is complete trash - seek out a Quick Change Station, located at the entrance of most regions and in the Sanctuary Ship.
Here you can not only swap out costumes and skins (as well as renaming both your character and FL4K's pets), but you can also reset all of your skill points to try building out a new style.
Of course, nothing is free in life - being able to respecialize your skills will cost a portion of your total money currently accumulated. A character with 29 thousand on hand will only have to pay just under 3 thousand to respect, while someone with 159k in their pocket will have to shell out 15k for a respec. It's a bit like dying - you always have to pay a portion to get what you want.
You've Got Mail
Please don't try to mail rocket launchers in real life.
It's easy to miss, but at certain points in the game, you may get a notification that you've received mail. Wait, what? Mailboxes in the game only have ammo in them, so where do you check your personal mail?
Head to the options screen and look for the Social tab among the Options/Play/Quit. It's here that you can skim through the different areas of the Social Menu to select your Mail, and obtain rewards given out by various NPCs in the game. Different gun manufacturers may give out presents when you've killed enough enemies with their weapons, and other characters may reward you with items as well when you achieve certain goals.
It's important to note that because the Mail is in the Social Tab - it's not tied to any one character - you'll be able to accept the gifts on any character you're playing as, even if they didn't do all the groundwork to get the gift in the mail. Note that the reward you receive from these in-game characters will be tied to the level you were when you unlocked the mail reward.
However, for those who have purchased a Special Edition of the game, you will also be able to redeem special unlocks and even Legendary Gear from your mail section. Legendary Rewards redeemed from the Special Edition will be tied to the level you are when you accept the gift - you may want to wait until you are a higher level to get gear that won't be quickly discarded.
Important: This is also the location where you will redeem all Golden Keys gained from entering Shift Codes in the SHiFT tab of the social options. They will not appear in your inventory until they are redeemed through mail.
If you've got a list of friends also playing, you can even send weapons you've found to them via the mail, in case you scored a really good class mod when playing on your own that your friend might want.

Borderlands 3 Equip Class Mod

A Weapon to Surpass Legendary?
6 million dollars and counting spent on slot machines - but still no row of hearts.
While Legendary Weapons are among the best you can get - they might not be the absolute best.
We haven't yet found this elusive tier, you may notice that one of the slot machines in Moxxxi's Bar has a payout for a 'red tier' weapon, which is above the payout for the 'orange tier' legendary weapon.
It is not yet known if these elusive red-tier weapons appear in the wild, or if they can only be obtained from the Slot Machines (or if the payout is actually a lie and you can't even get it anyways), but be sure to keep a lookout - and try not to spend all your money gambling!
The Mystery of Red Text
Though it doesn't list it - each shot fired from the Peacemonger will split into four explosive rounds that hurtle in different directions.
When you begin recieving quest rewards and finding uncommon or better loot in the world, chances are you'll notice many of these items will feature red flavor text in the gun's stats. These range from jokes to quotes to very strange words, but they do have meaning.
Like previous Borderlands games, the Red Text is usually a hint at the hidden nature of a weapon - especially for Legendary Weapons. Sometimes the ability is straightforward - like being able to see bullets explode into smaller pieces or follow a strange trajectory. Other times the abilities may be much harder to decipher - so play around with weapon that feature red text to figure out what features a weapon or item may be hiding.
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