Storage caves are all linked, and I think the space is infinite? Nobody can steal from them too.
Inns restore all your stats.
The quest board lets you earn spirit stones and Mayor Decrees. The latter is the currency for the manual pavillion. Keep in mind that the quests are tiered. If you breakthrough, you will get more difficult quests. In Area 4, Hell quests will be rough if you don’t have a full set of tiered and orange/red skills and passives. Resource quest will be easy since you will quickly have a large amount of items. Avoid the storage ring or assassination quests since that requires stealing/fighting and incurs NPC hatred.
Taverns can give you temporary boosts, increase affinity with random sets of people in town and let you trigger a small number of sidequests (purple exclamation mark).
Markets let you buy basic pills, minor breakthrough pills, rings and mounts, teleportation charms and some other items. They also have a set of books to learn for the specialization skills.
Every town has its own set of books for Feng Shui and Herbology, but not for Mining. So make sure you do a round and buy them all when you’re about to leave a region.
Cities (bigger, blue map icon) offer stuff for the second realm tier of a region.
Pavillions let you buy martial manuals. Usually only up to purple rarity. They require stones, mayor decrees and reputation (from quests). Cities have manuals for the second realm tier of a region. These can be decent if you broke through and need to update your skills. They will never have anything red and almost never anything orange.
Workshops cover forging and alchemy, which will be covered below. Synthesis lets you make qi pearls from fragments and upgrade the materials to cultivate skills if you need more.
You can buy the forging and alchemy recipes here.
Immortal wardrobe lets you buy new outfits. It’s largely pointless unless you really like one. You need to buy an item to start a time-limited monster fight for the drops to buy anything.
Auction Houses sell their inventory every 2 years, first month. They cannot be rerolled since their inventory actually comes from NPCs. You can sell tier-appropriate red/orange items here for a lot of cash. This is a primary source of red manuals, make sure to take a look. The manuals are usually only for the second realm of a region though.
During the auction, if you like something you can try outbidding the NPCs. Be warned that you can incur hatred here for outbidding someone, though this hardly matters. Furthermore the prices get pretty high, 10 times the sale price isn’t uncommon, make sure you have a lot of money.
NPCs seem to have a specific buy limit, so if you reload you can just bid that directly.
By the way, you can make the game skip all the items you don’t want anyway.
After the first region, Ascension Conferences are a pretty long tournament for the sake of Skill Fruits. They happen every 3 years. You can participate if you are in a sect, have a high enough reputation (do quests) and are in the later tier of a region. You should always participate since the Skill Point grind is dumb and you can get a lot of points at once.
You will be up against the strongest NPCs of the region, and rarely the world simulation may put you up against next tier NPCs. Make sure to drink up first. NPC victories are random, but weighed based on their stats, so rerolling can occasionally let you bypass a cheater.
By the way, there seems to be a minor bug where if you reregister immediately after a tournament ends, you don’t actually register. Let a month pass.
So why would you want to join a sect? It gives you access to the sect stores at reasonable prices for spirit fruits, lets you participate in the Ascension Tournament, gives you backing which can make NPCs not want to fight you, and access to techniques.
Joining sects is somewhat necessary. You get a letter of invitation for the very first from the prologue events, but you need to meet the requirements for the rest. That is either having the appropriate root or sufficient friendship levels. My impression is that befriending higher ranking people counts for more.
Then you need to go through a short tournament to actually join. It’s the same for when you want to get promoted. (Incidentally, it used to be that you might randomly have to fight NPCs of a tier or two higher that somehow were stuck in the sect. This made things occasioanlly frustrating.)
Your current sect will be a brighter icon on the map than the rest.
After you join one, you get access to a new currency, sect tokens. They’re gained from doing sect quests and are used to do basically anything in a sect. You also get a rank-dependent yearly salary.
In the first area, each sect controls 3 elements, in the others 2. They always have manuals and spirit fruits for these. Unfortunately, each region has an equal number of just and demonic sects, you can tell them apart by the design. Joining a sect with an alignment opposite to yours can be a hassle since you will be taxed on your sect tokens and may even suffer worse penalties like detainment. Sadly, each element is only ever present once, so if you’re in a region where the sect with your primary element has an opposite alignment, you’re out of luck. You can still befriend them for spirit fruits and get manuals elsewhere, so it’s not that bad.
If you wonder, the building levels seem to mean nothing.
The Treasure Pavillion lets you buy items. This includes the critical spirit fruits, for which sects are the only reliable source. This is also the only place to buy alchemy cauldrons (more later) and flames for refining artifacts. If you have joined a sect, all prices will be in sect tokens, if you have not, you can still buy items for spirit stones.
The prices for items will be greatly inflated if you haven’t befriended the sect however. If you want to get more access to spirit fruits, you will have to befriend the higher ranking people of the sect to make the prices sensible. This can also let you get an alchemy cauldron with better passive traits.
All other buildings can only be accessed by joining the sect.
The Manual Pavillion lets you buy manuals, mostly up to purple. If you get promoted to Grand Elder, you can access a set of red passives and ultimates for the elements of the sect. These can still be pretty useless though. Sects are largely not the best source of manuals.
Hospital lets you heal for free, Inns cost so little that this doesn’t matter.
The Cultivation chamber lets you trade sect tokens for Qi, this can occasionally be less annoying than hunting for Qi spots, especially in higher difficulties where they’re rare.
Council Hall lists the sects higher members, lets you withdraw your yearly salary and apply for promotion. The latter requires winning a tournament so check the NPC realms beforehand.
Mission Hall lets you do sect tasks for sect tokens. I’d suggest avoiding the Kill Sect Enemy task, since that just causes problems. The Rogue Cultivator is different, it’s not a named enemy. It’s only generated for the task and has no relationships. You can kill them without worry, but they can be tough.