Serves as an alternate download.

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This mod simply improves farming for items without adding new content or heavily modifying the game. This is done by implementing a pity system to a bunch of vanilla item drop rules. This mod serves as a proof of concept for a suggestion I made in the Terraria forums, which you can view here

How it works is simple. If a mob has a 1/400 chance of dropping an item, it is guaranteed every 400 kills. This applies for all enemy drop chances. A 1/7 drop chance is guaranteed every 7 kills, 1/13 in 13 kills. So on, so forth...

Additionally, if a loot pool is a selection of items (like the Moonlord's loot pool dropping 1 of 11 weapons), it will drop ALL of them AT ONCE when killed enough times. Kill requirement depends on the size of the selection (for Moonlord's case, 11 times). Though, keep in mind that these modified drop rules can stack! If a mob has a 1/2 chance to drop 1 of a selection of 4 items, it would take 8 kills to trigger both the guaranteed drops and drop all the items of the selection at once. This is calculated by multiplying the denominators of these two drop rules.

For example, killing 400 Chaos Elementals in an Expert mode world guarantees a Rod of Discord.
Don't believe me? You can try spawning 400 Chaos Elementals with Cheat Sheet in an Expert mode world yourself and a weapon of choice (other than butcher commands) and it will ALWAYS drop a Rod of Discord every 400 kills!

This also applies for treasure bags and loot crates but they might be inconsistent when the loot table is really big. Though, this lead to a side effect of getting way more dev sets than you'll ever need... (Unless you want to use or sell them)

Tested with most content mods. Here are some notable finds:
-Boss masks are always dropped every 7 kills as most of them are 1/7
-Bosses in Fargo's Souls will always drop their corresponding weapon every 10th kill as they are a 1/10 or 10% chance (3rd kill in Eternity mode as it is 1/3)
-Calamity bosses always drop their Revengeance weapon (like Malachite from Plaguebringer Goliath) every 10 kills as they are a 1/10 or 10% chance
-Bosses drop all 3 Revengeance mode accessories (Laundunum, Stress Pills and Heart of Darkness) at the same time after 60 kills, as it is a 1/20 with a selection of 3 items, making it a 1/60.

Things it doesn't work with:
-Custom drop rules that do not extend CommonDrop, OneFromOptionsDropRule or OneFromOptionsNotScaledWithLuckDropRule
-Most Calamity treasure bag drops (other than Revengeance drops) as they already use a pity system

Other features:
-Anti back to back invasions: Prevents back to back natural invasion events of the same type, unless the event has a 100% chance of occuring (like Celestial Pillars and Calamity's Acid Rain)
-Anti back to back natural events: Prevents back to back Blood Moons, Solar Eclipses or a mix of both or with other naturally occuring events

This mod is configurable, you can tweak some of the pity rules if you want!

Bad Luck Protection (Pity System)