I've been sinking some time into this game for the past few days, started a new world once again. Up to this point I was very reluctant to make a world enter Hardmode, due to the inevitable clusterfuck that would ensue as the Corruption and Hallow spread out of control. As a result I have little experience with Hardmode, but figured I'd just roll with it...which proved to be a blessing in disguise as I went through some hilarious moments.
# Expert Mode is Love, Expert Mode is Life. The improved loot drops from the bosses (and some monsters) makes it all worthwhile. The Worm Scarf alone (17% damage reduction) is awesome, but the Demon Heart (adds a sixth equipment slot to your character) is the true Prize. Everything written below assumes you're playing in Expert Mode.
# Hardcore Terraria however, is like masturbating with a cheesegrinder. Expert Mode Hardcore Terraria switches out the cheese grinder for a combine harvester. Not really worth the bother.
# As mentioned earlier in this thread, keep a steady supply of Dangersense Potions on-hand and active at all times while exploring the Underground. I died countless times to boulder traps and the new "landmines" - you can tell them apart from other traps by the short, straight vertical wire.
# The Dangersense potion is rendered obsolete the moment you recruit the Mechanic. She sells a Mechanical Lens that allows you to see wires in-game by merely having it in your inventory. Better yet, buy all four Wrenches and a Wire Cutter to make a multi-purpose Wrench, then combine that with the Ruler (from the Goblin) to make the Grand Design, the Final Word in all things wiring-related.
# Getting a Grappling Hook is one of the first big steps of advancement for a new Terrarian, but the upgrade tree for them is off. To make the standard one you need some chain and a hook, and hooks only come as drops from a couple of monsters in the mid-layer Underground. But another option is to spend 15 gems to get a Grappling Hook of the respective gem type that doesn't require a hook for some reason...and except for the amethyst version they're all better than the standard Grappling Hook. "But gems are rare and valuable!" you say? Extractinator has got you covered. As a result it's quite probable that a player will have the respective gems needed before he ever lays his hands on a hook. Diamond Grappling Hooks are the best, but diamonds are also the rarest gem. A decent middle-ground is to craft an emerald Grappling Hook, it's better than most pre-Hardmode hooks.
# In the early game I tend to go for melee builds, and getting the Katana from the Traveling Merchant should be a early-game goal for everyone as it's a poor man's Muramasa. If you're lucky to get an Enchanted Sword, you're set up until the Night's Edge.
# When life gives you Pink Gel, open up a brewery and make Molotov Cocktails. Lots and lots of Molotov Cocktails.
# If you want to buy Lost Girls a drink, buy them Molotov Cocktails. Lots and lots of Molotov Cocktails.
# The Medusa may be gone from early-game Marble biomes, but the Hoplite is still a force to be reckoned with. Those Javelins of his
hurt - I suggest avoiding marble biomes until you're at least capable of taking on the Eye of Cthulhu.
# I had to spend considerable effort to be battle-ready against the Eye of Cthulhu, and I almost didn't survive the fight. Skeletron took 3 tries. The Eater of Worlds, by comparison, was a cakewalk and I barely lost any health. Queen Bee takes time and patience to put down, but King Slime came so early that I died over a dozen times just to take him out once. In all cases, building platforms to give you vertical fighting space is a Good Idea.
# There are tons of potions in this game, but the 2 most important ones are Regeneration Potions and Ironskin Potions.
Always keep a stack of these at the ready.
# As Expert Mode robs you of 75% of your carried money upon death, it's a very good idea to get your hands on the Money Trough (remote access to your Piggy Bank). They drop from Blood Moon zombies, so start farming those until you get one. The "Oink!" sound it makes is worth the effort alone.
# Previously, whenever I needed Obsidian, I'd re-route lava and water in the Underground to meet each other. This time around I actually crafted and used a bucket for the first time, and now I feel like an idiot (Part 1). Craft a bunch of them and you can carry lakes of liquid in your pocket...and water buckets poured on your head are just the thing to cancel out the "On Fire!"-debuff, which can easily kill you in Expert Mode.
# There's a new trap down in the bottom-layer Underground: Geysers. Step on the pressure plate above, and a plume of fire shoots up, not unlike the Lizharhd Fire Traps. Didn't take me long to find a bunch of them and rig them up at my base as a poor man's Death Pit. I just hooked them up to a lightswitch, but in hindsight I may have been better off using a Yellow Pressure Plate, as those are triggered by everyone
but the player.
#
Hirato mentioned this almost 3 years ago, but Gravitation Potions are THE best way to find floating islands. I feel like an idiot (Part 2). Try to get a zig-zagging pattern going to cover more grou...er...air.
# In Hell I tend to make a (very very long) runway out of platforms to fight the Wall of Flesh and have a generally easier time to move around. If you're like me, you need to use Obsidian Platforms as they're the only platform that's immune to lava. Fortunately there's plenty of them in Hell itself, and the black houses are made of Obsidian bricks, which is the material needed to make more platforms.
# A good tip for fighting the Wall of Flesh: Finish it off with the Star Cannon. Use whatever means you prefer to get it down to low health, then whip out the cannon. The lower its health gets, the faster the Wall moves, up to the point that it moves faster than you ever could, so that's the time to bring the pain.
# With Hardmode enabled and far too much money in my Piggy Bank, I started experimenting with what (the new) NPCs were now selling, to the point that I visited prior worlds to see what lay ahead for me (I'm honestly scared with facing the Hardmode bosses in Expert Mode). This led to a new discovery: I had previously known what the Clentaminator did, but it's only now that I realized what the Green Solution does. Part 3 of me being an idiot.
# In my "off-world" experimentation, I experienced a Solar Eclipse event. I don't know why Nailhead has 4000 HP, but the Psycho enemy managed to kill me
twice before I realized what his gimmick is. That's just fucking evil...
#...but not as evil as the grin on my face when one of the Psycho enemies dropped his knife. I now have a decent damage-dealing weapon that renders me
invisible when I wield it! I'm going to have fun with this...
# Green Jellyfish and Arapeimas are NOT to be underestimated. You ARE gonna need a bigger boat.
# From what I gather there's really not much point going back to Hell once Hardmode is unlocked. There is one good reason to go back, however. Bring Purification Powder along.
# Lulziest moment of the game: Going through my stuff I find I have just enough souls to craft a "Key of Night". I make one, and (wrongly) think that I finally have the means to open those funky chests in the Dungeon. Nope, they need a different key. Disappointed, I warp back to base and while sorting through my accumulated loot I stick the Key of Night into an empty chest...all I'm gonna say is: Try it yourself.
Probably more later.