Core Crystal

Core Crystals are a type of item in Xenoblade Chronicles 2. Drivers can resonate with Core Crystals to awaken Blades.

Standard Core Crystals
The following Core Crystals will grant their driver a random Common Blade or Rare Blade.
 * Common Core Crystal
 * Rare Core Crystal
 * Legendary Core Crystal

Unique Core Crystals
The following Core Crystals are unique and will grant their driver a predetermined Rare Blade.
 * Unnamed Core Crystal
 * Beastly Core Crystal
 * Sealed Core Crystal
 * Roc's Core Crystal
 * Vess's Core Crystal
 * Lucky Core Crystal
 * Praxis's Core Crystal
 * Theory's Core Crystal
 * Aegaeon's Core Crystal
 * Ebullient Core Crystal
 * Divine Core Crystal

Mechanics
The formula for pulling Rare Blades is as follows: Probability (in %) = ((√(Luck) *0 .01 * 1.3) + .95) * 0.01 * (100 + 5 * [Highest Idea Level]) * [Core Crystal Multiplier] * [Base Probability]

There are five variables that determine the likelihood of a player pulling a Rare Blade.
 * A Blade's Base Probability
 * Core Crystal Rarity
 * The Idea Cloud
 * The Driver's Luck stat
 * The Pity System

Base Probability
When a new game is started the player will be assigned one of 4 potential groups. Although 5 groups exist, due to an error in Xenoblade Chronicles 2's code the first group was repeated, causing the fifth group to go unused. Each group grants every Rare Blade a base probability, which is the chance a Player has to pull the rare blade without any form of external factors. These base probabilities are different for every group, with Sole exception of KOS-MOS who always has a .1% base probability.

Core Crystal Rarity
The rarity of the Core Crystal used will directly impact the player's chance of pulling a Rare Blade.
 * Common Core Crystals have a 1x chance of pulling a Rare Blade
 * Rare Core Crystals have a 1.5x increased chance of pulling a Rare Blade
 * Legendary Core Crystals have a 3x increased chance of pulling a Rare Blade

The Idea Cloud
The bonus granted by a driver's idea cloud is calculated with the equation: 0.01 * (100 + 5 * [Highest Idea Level])

Whichever stat on a driver's Idea Cloud is highest will grant the driver increased odds of pulling Blades of the associated two element types. For example: if a driver's highest idea stat is Bravery, then they will have increased odds of pulling Blades of the fire and water elements. Only the highest idea stat is taken into account. In situations where two or more idea stats are tied for the highest, ties are broken randomly. Through the use of a Booster, a player can temporarily boost the idea stat of a specific driver. This will have the game treat the idea which was boosted as the highest one, regardless of its given level. The maximum benefit the Idea cloud can grant is a 1.75x bonus to pulling Rare blades when an Idea stat is at level 15.

The Driver's Luck Stat
The bonus granted by a Driver's luck stat is can be calculated with the equation: √(Luck) * 0.01 * 1.3) + .95

The maximum luck a driver can have is 999, which will grant 1.36x bonus to pulling Rare blades.

The Pity System
Every time the player uses a Core Crystal they are granted a set amount of "pity points".
 * Common Core Crystals grant 5 "pity points"
 * Rare Core Crystals grant 25 "pity points"
 * Legendary Core Crystals grant 50 "pity points"

Once a Player has accumulated 100 total "pity points" the next Core Crystal they open will contain a Rare Blade determined by their assigned group. Another Rare Blade is obtained at 200 "pity points," and a third is obtained at 300 "pity points." After pulling any Rare Blade, either through the pity system or naturally, their "pity points" reset.

Trivia

 * Although most party members can use Core Crystals, Tora, Vandham, Jin, and Malos are all unable or unwilling to resonate with Core Crystals.
 * If the player releases a Blade that is originally from a unique Core Crystal, they will be added back into the pool of Rare Blades and can be pulled from Common, Rare or Legendary Core Crystals.