The Binding of Isaac: Rebirth – Retribution – advanced item Guide

Death Cap

 
Official description: 

Damages the player and grants the following stat changes per bite: 
-0.35 damage, -0.06 speed, -0.06, shotspeed 
+5% chance to fire poison tears 
 
Once fully consumed, grants major stat upgrades and full health: 
+2.75 damage, damage x1.5, +0.5 speed, +0.5 shotspeed

Additional info: 

• Takes 6 bites to fully consume. Will not hurt you on the 6th bite and will fill 11 heart containers instead. 
   
• Assuming you have Isaac’s starting stats, you’ll end up with 1.75 damage, 0.7 speed and 0.7 shot speed after the fifth bite. Using the item again will increase that to 6.75 damage, 1.20 speed and 1.20 shot speed. 
   
• Getting damaged by Death Cap will count against devil deals, will get doubled on the Womb floor and will not take red hearts before soul hearts. Basically, it works like damage from monsters, not items like Razor Blade or IV bag. 
   
• Damage from this item is affected by invincibility from things like Chariot card, as well as regular invincibility frames. If you have a battery on the floor, you can use Death Cap, quickly recharge it and use it again without getting hit! 
   
• Works as expected with Car Battery. You can consume the mushroom in 3 bites, but you’ll receive x2 debuffs with each use. Will only damage you for half a heart, however. 
   
• If you suck up Death Cap with the Void, it will replace Void upon the next use of it.

Black Box

 
Official description: 

+4 luck whilst holding, reduces luck by 0.5 each use. 
Chance to spawn either spiders or an item proportionate to luck.

Note: the official guide says that it spawns a “collectible”, but I changed it to “item” for clearance purposes. I thought that it’s just a luck-based version of the Book of Sin when I first read about it. 
 
Additional info: 

• Black Box depends on current room’s item pool. You’ll get shop items if you use it in a shop and angel items if you’re in an angel room, for example. 
   
• You can use Black Box an unlimited amount of times and get multiple items from it. 
   
• The formula for calculating whether you get the item or not is:
  if math.random(100) <= (p.Luck * 5) then blah blah blah spawn a random item

  …meaning that you have 5% of getting an item per 1 point of luck. Each use of this item reduces that chance by 2.5%. 
   

• If you have 0 luck or lower, you have no chance of getting anything from Black Box, besides spiders. At 20+ luck, you have a 100% chance of getting an item. 
   
• Since carrying the Black Box gives you +4 luck, the base chance of getting an item is 20%. I recommend not using it until you increase your luck. 
   
• Dropping the Black Box will give you -4 luck and will not replenish the negative luck you’ve gained by using it. 
   
• Works as expected with Car Battery. Using Black Box will lower your luck by 1 instead of 0.5 and you’ll get 2 shots at getting an item. In theory, you have a higher chance of getting an item like this since both rolls probably depend on the same luck value, but I doubt that it’s possible to prove this.

Modelling Clay

 
Official description: 

Copies the passive item or familiar nearest to the player. Resets at the beginning of each floor, removing the granted item. 
The granted item is also removed if Modelling Clay is dropped or swapped with a new active item.

Additional info: 

• Can be used on paid pedestals in shops and devil deals. 
   
• If the copied passive item does something to your health, gives you consumables or spawns pickups, that effect will not be reverted upon entering the next floor, much like when you reroll your items with D4. 
   
• If the copied passive item belongs to a transformation, your progress towards it will remain after the item is removed. However, picking up the item after you’ve duplicated it will not yield you additional progress. 
   
• Most resurrection items get removed as you would expect them to, so if you decide to duplicate one, you’ll have to die on the same floor. The exception to this is Dead Cat, which will grant you 9 lives, but will lose one when you enter the next floor. This only happens once. 
   
• Items that trigger effects when you enter a new floor will do that before they get removed. Some examples of these items are: Missing No, Bar of Soap, Guppy’s Pride etc. 
  Speaking of Guppy’s Pride, the familiars generated by it will not get removed upon entering the next floor since they’re not actually tied to the item. 
   
• Car Battery doesn’t do anything with Modelling Clay. 
• You can’t use Modelling Clay multiple times with the ? card. 
• If you suck up Modelling Clay with the Void, it will replace Void upon the next use of it. 
• Using Diplopia on Modelling Clay will not do anything spectacular, since “the granted item is removed if Modelling Clay is swapped with a new active item” 
• If you duplicate School Bag, it will get removed on the next floor and the second active item will be dropped on the floor.

False Idol

 
Official description: 

Grants +10.9 luck for the current room.

Additional info: 

• If you use this item 2 times without exiting the room, it will, on top of granting more luck, drop the False Promise, which is a passive item that gives you +1.09 luck. This only works once in a run, though. 
   
• Black Box synergizes very well with this item, especially if you can use either one of them multiple times before leaving the room.

Lent

 
Official description: 

Picking up no hearts on a floor grants full health and +0.5 damage upon starting a new floor.

Additional info: 

• Right now the item is bugged and will grant you a damage up even if you pick up hearts.

Turnip

 
Official description: 

Mimics a Stalk Market pattern with your coins each room. 
Rots after 7 rooms or upon being dropped. Regenerates on the next floor.

Explaination: 
This trinket is a reference to Animal Crossing’s feature called “Stalk Market”. If you’ve played Animal Crossing – great, you don’t need my explaination! However, if you’re like me and that’s not the case, I’ll try to explain what the Stalk Market is. 
 
As the name implies, it’s Animal Crossing’s stock market. Using it, you can buy and sell turnips for a certain price that changes every day, in order to profit. The idea is to buy turnips when the price is low and sell them when it is high. However, if you hold onto your turnips for a couple of days, they will rot and you’ll lose a lot of cash. The market prices seem random at first, but can be easily predicted if you know what you’re doing because they always follow 1 out of 4 “trends”. 
 
This trinket works similarly. When you first pick it up or enter a new floor with it, it gets affected by 1 out of 11 possible trends (see below) and follows it until you enter 6 rooms or drop it. 
 
Upon entering an uncleared room, the trinket will change the amount of money you have, depending on the current trend. When you enter the 7th room, the turnip won’t change how many pennies you have and will rot. Here is the list of all possible trends: 
 
 
 
Looks pretty confusing, right? But don’t worry, it’s actually easy to understand. As we can see, there are 11 arrays, which are called “trends”. Every one of these 11 trends has 12 numbers, divided into 6 pairs for 6 rooms. These “pairs of numbers”, divided by slashes, are actually fractions. They are used to calculate the percentage which will be applied to your amount of money when you enter the next room. 
 
When you enter the first uncleared room on a floor, Turnip will randomly pick one of the 11 first fractions and will multiply your money by it. After you enter the next room, it will do the same thing, but with the second fraction from the same trend, then the third, fourth, fifth and sixth. After that, the trend will be over and the turnip will rot upon entering the 7th room. 
 
So, what do we do with this knowledge? Normally, you would just wait until the trinket gave you more money than you started with, drop it, pick it up and repeat the process on the next floor. But now that we know how Turnip works, we can use it to its full potential by figuring out what trend it follows and “predicting the future”. 
 
Finding and abusing the correct trend: 
In order to explain how to find the current trend, I will use an example. Let’s say that I entered a new floor with 40 pennies and the turnip trinket. I walk into the first uncleared room and my money gets set to 42. Since 40 pennies was 100% of my money and now I have 42, I can find the percentage that was applied to my money by using the following formula:

Now that I know the first percentage of the trend, I can take a look at the list of trends and see that only 3 of them start with the fraction 105/100 (which is equal to 105% that I got). As such, I will cross out the rest and focus only on these ones. 
 
When I enter the second room, my money gets reduced to 39 pennies. I look over at the 3 trends that I picked and notice that the next possible fractions are 78/105, 97/105 and 75/105. The middle one seems to be more fitting than the rest, so I decide to check it. I divide 97 by 105 and get ~0.923 as a result. Then, I multiply 42 by this number (because that’s the amount of pennies that I had before I entered this room) and voila! I get 38.79, which is very close to 39 pennies that I currently have. Now I know that the Turnip’s trend for this floor is Small spike – 1 and I’m ready to make some money with that knowledge. 
 
 
 
Let’s take a closer look at our array of fractions. Since improper fractions are equal to values higher than 100%, they are what we’re looking for. 
{105/100, 97/105, 89/97, 120/89, 195/120, 100/195} 
 
After inspecting the trend, we now understand that, in order to get the biggest payout, we should go through 5 rooms and drop it before we go into the 6th one. 
 

 
Note: 

• Since we’re always working with small numbers in Binding of Isaac, sometimes this method can be inconsistent. In order to avoid this, if you get 93%, 95% or 96% as the first percentage of the trend, keep all trends that start with those values. Do the same with 85% and 86%.

The end

 
Thanks for reading! Hopefully this guide was helpful for you. As I said in the beginning, feel free to leave your suggestions in the comments, if you have any. 
 
Spent 11 hours making this, jesus christ. 
 

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