Luck

Luck is a hidden modifier on random rolls. It never appears in the interface; the closest thing to a readout is the Wizard, who occasionally swaps his usual chatter for a rough estimate. The value bottoms out near -1.1 and tops out at 1.76, though nothing above 1.0 does anything, so 1.0 is the real ceiling.

The mechanic edits the odds, not the outcome. With positive luck L, every affected roll has an L times 100 percent chance of having its denominator rewritten: 1 in X becomes 1 in Y, where Y falls somewhere between half of X and X minus one. At luck 1.0 that happens on every roll. Negative luck mirrors it, pushing the denominator toward twice X.

For anything rarer than a few percent that collapses into a rule of thumb: full positive luck yields roughly 40 percent more drops over a long farm, and full negative luck costs about 30 percent.

• Enemy drops, including hearts and mana stars. The luck used is that of whoever was closest to the kill.
• Rare spawns: golden critters, Truffle Worm, Prismatic Lacewing, Enchanted Nightcrawler, mimics, fairies, gnomes, Dungeon Spirits and the bound NPCs.
• Coin drops from enemies, worth roughly 15 to 19 percent more at full luck. In Classic that includes bosses.
• Fishing power, silently. There is a chance per cast that your power is multiplied by anywhere from 110 to 140 percent.
• Damage rolls. Every hit already varies by 15 percent either way; luck adds a chance to roll that variance twice and keep the friendlier number, both for damage dealt and damage taken.
• The Traveling Merchant stock list, Coin Portals from pots, and the odds of a Hardmode Dungeon enemy appearing on the wrong wall type.

Anything from a bag ignores luck entirely: crates, Oysters and Treasure Bags. That last one matters. In Expert and Master every boss drops a bag, so luck does nothing at all for boss loot above Classic. Guaranteed one from a list drops are exempt too, so stacking luck before a Mimic will not steer which weapon falls out.

Also unaffected: fishing catches beyond the power number, Angler rewards, dodge chances, ammo conservation, event timing, and health and mana regeneration.

Torches only move the number in the underground layer and below, and only inside an 81 by 81 tile box centered on you. One correct torch is the entire bonus; a second adds nothing and one wrong torch cancels it. The floor is zero, so torch luck can never drag you negative on its own.

Biome torches pay off in their own biome and penalize you everywhere else. A plain torch penalizes you in any biome that has a themed torch, and the bone torch is the fallback that pays in biomes with none of their own, plus the Ocean. Hybrids are forgiving: an ice torch and a hallowed torch together in hallowed snow both count.

Above ground and in space only a torch in your hand counts, since placed ones are ignored up there. The Dungeon and the Jungle Temple opt out of torch luck entirely, and switching a torch off with wire does not exempt it. Torch God's Favor converts plain torches to the right variant as you place them, which removes the most common way to lose the bonus without noticing.

Getting close to a naturally spawned ladybug grants good luck that decays to nothing over twelve minutes, doubled for a gold ladybug. Distance is punishing: full duration needs you almost on top of it, and the falloff is a sixth power curve out to fifty tiles, so at half that range you get near nothing. Killing one, or using it as bait, does the reverse for three minutes, six for a gold one.

Killing a town NPC costs a little luck for a minute. Two are exempt: the Clothier, and the Guide, whose death counts as good luck for four minutes. Bad ladybug luck overrides good, never the reverse, and refreshing either keeps the longer timer rather than adding them. It all resets when you leave the world.

Throwing coins into Shimmer destroys them and charges a counter shared by everyone within about 62 tiles. One copper is one point, the counter caps at a million, and a single platinum coin fills it. A full counter is worth 0.2 luck for a little under four minutes, then steps down by 0.025 every six and a half minutes.

The counter burns faster whenever you speed up time, so sleeping in a bed or running an enchanted sundial eats it. It survives death and resets when you leave the world. Spend a coin at the start of a specific farm rather than trying to keep it topped up.

Reaching 1.0 is straightforward. A garden gnome at the farm, a greater luck potion, the correct biome torch in range, and a Lantern Night if you get one will carry you there. The lucky coin is unrelated despite the name and does nothing for this stat.

Then remember the shape of what you are buying. Luck is for enemy drops, rare spawn hunts and long grinds. It is worthless against a boss in Expert and for crate fishing.