Hardmode

The first time the Wall of Flesh dies, the world changes permanently. Two diagonal stripes are carved from the sky down into the underworld in a rough V, one converting everything it touches to Hallow, the other to whichever evil biome your world was generated with. Tougher enemies start spawning immediately, but the terrain conversion runs in the background and finishes a moment later, sooner on a small world than a large one.

There is no undo short of an outside editor, and both the Hallow and the evil now spread on their own. If you want a pre-hardmode world to keep, back it up first.

Every new enemy has several times the health and damage of what you were fighting, and on Expert and Master the old enemies get scaled up too. A Blue Slime that had 50 health pre-hardmode carries 274 on Expert and 411 on Master. Low-tier hardmode weapons start around 40 damage, so the gap between your current gear and the floor of the new tier is real.

The fix is reforging rather than shopping. Money spent on prefixes for gear you already own will get you through the first ore tier. What holds up is a short list: Nights Edge, Sunfury and Flamarang for melee, Molten Fury and Phoenix Blaster for ranged, Flower of Fire and Flamelash for magic, Spinal Tap and Imp Staff for summoners.

Two places stay calm for a while. The underworld keeps its old spawns until a mechanical boss dies, and the dungeon keeps its own until Plantera does. If the Wizard, Goblin Tinkerer or Tavernkeep are still unfound, go now while the trip is survivable.

The Pwnhammer is your reward for the Wall, and its only job is breaking altars. Each of the first three you smash seeds one tier of hardmode ore into the world, and which of the two options you get is not rolled until that altar breaks. The first gives cobalt or palladium, the second mythril or orichalcum, the third adamantite or titanium, and once decided the alternate never appears in that world.

Breaking more altars restarts the cycle at reduced yield. The fourth through sixth produce half as much as the first three, the seventh through ninth a third, and so on down. Twelve altars roughly doubles the original allotment and thirty-three roughly triples it. The rarity order never shifts: cobalt and palladium stay common, adamantite and titanium stay scarce.

Each tier gates the next, so the order is not optional. A Molten Pickaxe opens cobalt and palladium; those pickaxes or drills open mythril and orichalcum; those in turn open adamantite and titanium. The crafting stations gate you as well. Most of the better hardmode recipes need a mythril or orichalcum anvil, and turning the top ore into bars needs an adamantite or titanium forge built onto a hellforge.

Chlorophyte Ore sits past all of it and needs a Drax or Pickaxe Axe, built from Hallowed Bar and a soul contributed by each mechanical boss in turn. Hardmode crates fished up now hand you ore and bars directly, but crates saved from before the Wall only ever give pre-hardmode loot.

Chlorophyte converts adjacent mud into more of itself, at any depth once seeded, not only in the jungle. Wall off a room of Mud Block somewhere convenient, plant a few pieces, and come back to a renewable supply instead of tunneling the jungle again. After Plantera it feeds both upgrade paths: Shroomite Bar through the Autohammer the Truffle starts selling, and Spectre Bar by combining it with Ectoplasm from the dungeon.

Queen Slime is optional and sits comfortably between the first ore tier and the mechanicals. The three mechanical bosses can be summoned at night or roll a nightly chance to appear on their own once an altar is down. Killing any one of them starts Life Fruit growing in the jungle and brings the Steampunker to town. All three unlock Plantera, Plantera drops the Temple Key for Golem, and Golem brings cultists to the dungeon door, which leads to the pillars and Moon Lord.

Duke Fishron and Empress of Light unlock long before you should fight them and both expect post-Golem gear. The Empress carries a trap: in daylight every one of her attacks kills outright, whatever your defense.

Her death halves the spread rate of the Hallow and the evil, the single biggest quality of life change in hardmode. It also repopulates the dungeon with far harder enemies, brings in the Cyborg, opens the temple, and unlocks the Pumpkin Moon, the Frost Moon and the biome chests you have been walking past.

Hardmode runs on drops rather than chest loot, so build farms early. Hold onto iron, lead, bones, lenses, vertebrae and rotten chunks, because the mechanical summons all eat them and a spare pre-hardmode world is the fastest way to restock.

For coins, Crystal Shard grows back on exposed pearlstone, so mining stripes through the underground Hallow gives you a route to walk. Farming The Destroyer is the other option: it dies fast to melee, costs no ammunition, and its bars and souls turn into Light Disc that sell well.