Iben Fahd’s Tenacity
Each and every chest you open in Iben Fahd’s sanctum has exactly the same chance to drop the Tenacity item.
That chance is 1%, as shown in-game…
Chance that a chest contains the Tenacity item = 0.01
Chance that a chest does not contain the Tenacity item = 0.99
Chance that none of X chests contain the Tenacity item = (0.99)^X
Some example values of X…
- Chance that none of 5 chests contain the Tenacity item = (0.99)^5 = 0.95099
- Chance that none of 10 chests contain the Tenacity item = (0.99)^10 = 0.90438
- Chance that none of 25 chests contain the Tenacity item = (0.99)^25 = 0.77782
- Chance that none of 50 chests contain the Tenacity item = (0.99)^50 = 0.60500
- Chance that none of 100 chests contain the Tenacity item = (0.99)^100 = 0.36603
- Chance that none of 250 chests contain the Tenacity item = (0.99)^250 = 0.08105
- Chance that none of 500 chests contain the Tenacity item = (0.99)^500 = 0.00657
There is no value for X which guarantees the drop, just that higher values of X make it increasingly unlikely that you won’t have found the Tenacity item after opening X chests.
To give an idea of how rare this actually is, let’s look at that 250 chest line there.
A full clearance of the Sanctum, i.e. 25 chests, requires 377 keys.
So, 250 chests is 3770 keys’ worth of chests, which is many, many months’ worth of keys.
Even with that many, roughly 1 in 100 players still wouldn’t get the Tenacity item.
–==[ EDIT ]==–
Updated the thread to use a different picture hosting website, as imgur no longer makes content available to devices having UK-based IP addresses.