Have you ever tried to get 100% physical resistance by using a Stone Skin Amulet and a Might Ring, only to be surprised that you still take damage?
This article should help you better understand how resistance items work.
So how do resistances work?
The main difference to how most people have presumed it works is that each resistance is applied one after the other, rather than at the same time.
Here is a quick example with a Stone skin amulet and a Might ring when taking 100 damage:
The Stone skin amulet will resist 80% of the attack, meaning that it is now 20 damage, and then the 20% from the might ring is applied to the 20 damage, meaning you end up with 16 damage which is equivalent to 84% resistance , rather than just adding 80% and 20% to give 100% resistance.
Also, after each resistance item is applied, the damage you recieve is rounded DOWN to the nearest whole number.
An example of this is if you wore terra legs and a terra hood (6 and 4%) earth resistance, and stepped on a poison field which deals 5 damage:
First, the legs 6% resistance is applied.
94% of 5 is 4.7, which gets rounded DOWN to 4.
Next, the hoods 4% resistance is applied.
96% of 4 is 3.84, which is again rounded DOWN to 3.
From this you can see you blocked 40% of the damage from poison field, when your total resistance was only 10%.
To find out what % damage you will block make each resistance item into a decimal to show how much of the original damage you will take while using it, eg might ring blocks 20% so the decimal would be 0.8, magma boots block 5% so the decimal would be 0.95, etc...
Then multiply them together and take this decimal from 1 to give you the amount of damage you will recieve as a decimal of the original damage. An example of this can be seen in the next section.
What implications does this difference have?
Well for most situations, the difference isnt that large to the previous way of calculating.
So if you wear Lightning headband (4%), robe (8%), legs (6%) and boots (5%), you will block 21% (0.96 x 0.92 x 0.94 x 0.95= 0.79) opposed to 23%, a difference of a mere 2%.
On the one hand, if you aim to get a very high resistance, for example on certain quests, it may make a large difference (and not in your favour) as shown in the previous Stone Skin amulet and Might ring example.
On the other hand if you recieve low but frequent damages, such as walking over elemental fields, or taking duration damages, it can make a significant difference (in your favour)!
Wearing Terra hood, mantle, legs and boots will mean you only take 1 damage from poison fields, for 4 turns. Wearing a Magma monocle, dragon robe, magma legs and boots will mean you take only 13 damage from fire fields, and 5 from the smaller ones.
It also means, that items that give a % bonus to physical resistance will always block a minimum of 1 more than the armor has blocked and will block on average 0.5 damage better than expected (for hits that get blocked by more than 1). From this, wearing a Zaoan helmet (arm 9) and Zaoan legs (arm 8) will ALWAYS block more than Demon helmet (arm 10) and Golden legs (arm 9), even if you get hit for 3hit points.
Methodology
The reasearch was done by using a trap that dealt a consistant 200 earth damage when triggered.
This way gave precise results each time, without needing to take averages.
At first it became apparent that the resistances multiplied instead of stacked, however the damages that were recieved were sometimes 1 or 2 off from the expected value, which was found to be due to the rounding down after each item.
Example of how to use the research results in practice
Some may ask: As a Mage, should I use resistance items or magic level bonus items (such as focus cape and yalahari mask)?
Well as usual, it depends on the situation. Generally, if you dont take many physical hits, having a magic level bonus is more economical than having resistance items. However, having good resistances can DRAMATICALLY improve your chances of survival!
For example if you are a mage fighting frost dragons from a distance, you can get yourself 20% resistance to both ice AND life drain (when their strongest attack, smoke wave, deals life drain damage). You can gain this by using the Glacier set aswell as a garlic necklace. For a lv100 mage, this is the equivalent of having 160 MORE hp  which is 40 levels!.
If you often take elemental damage, and have a chance of getting spammed resistance items are probrably best, otherwise you can use Magic level bonus items.
