Core Crystal

Core Crystal is a round core surrounded by an octahedral energy shield that resembles a crystal. In Mega Man X4, after Colonel is destroyed by Zero, Iris is filled with grief and salvaged Colonel's memory chip (カーネルの記憶チップ), incorporating it into her and turning into a combat Reploid that resembles a Ride Armor. While she became as powerful as her Repliforce developers had originally expected, the programs of the siblings enter in conflict and Iris runs out of control. In this form, Iris herself doesn't take damage, but after taking enough hits, the core will be released from her body and assist her by releasing a laser under her opponent when Iris fires a laser from her cannon. The core must be destroyed to stop Iris, returning her to normal. However, the damage caused by combining herself with the core was high, with Iris passing away shortly after.

Rockman X DiVE
Core Crystal (核心水晶), known as "Water Play Dream" (水遊の夢) in Japanese, is one of the active skills from Swimsuit Iris. When used, Swimsuit Iris summons a Core Crystal that will shoot out a water jet in front of her and deal damage continuously to all targets in range. The water jet disappears after six seconds. It has three skill cards that can improve the skill, but only one can be equipped at a time:
 * High-Pressure Water Jet - Damage register accelerated by 20%.
 * Water Spray - Increases range by 25%.
 * Quick Charge - Reduces preparation time by 20%.

When Swimsuit Iris is fully upgraded, the passive skill Double Water Jets becomes available. When unlocked, the skill will summon an additional Core Crystal under the target and unleash a water jet that shoots upward, causing damage to targets in range. This makes it similar to the Laser attack used by Iris in Mega Man X4 when the core appears.

TEPPEN
The core is visible floating above Iris in the card Tragic Rampage.

Shironeko Project
Core Crystal, also named Crystal Core (水晶核心) in the game, is a skill from Iris. When used, Iris and the Core Crystal rise in the air and the core unleashes a giant laser forward that causes continuous Dark damage and has a chance to stun targets. Iris can freely move in any direction while using the skill, allowing it to hit multiple targets. When using her Swimsuit Iris skin, the Core Crystal skill becomes Core Crystal (Water) (核心水晶（水）), the core being replaced by a beach ball with Zero's face and releasing a giant water jet that causes Water damage.

The Core Crystal is also used by her in the skill "Delivering a Wish for Peace" (傳遞和平心願). Iris rises the core in the air and launch it forward, the impact causing a huge explosive. With her Swimsuit Iris skin, the skill changes to "Conveying the Feeling of Love" (傳達愛慕心情), the core being replaced by a beach ball with Zero's face, and Iris jumping to hit the ball in the air, throwing it and causing a large splash on impact.

In the Rockman X DiVE Project event story, the Core Crystal was malfunctioning and Iris could not use it properly, so the blacksmith Baron modified it into a magic weapon, allowing Iris to use it akin to a mage's rod. This weapon could be obtained during the event and can be used by any mage. When upgraded, the weapon gains the skill "Iris's Daydreaming" (愛莉絲的白日夢), which provides buffs. The animation of Iris's Daydreaming depicts the mage floating in the air then falling, being caught by the team's leader (by the next character if the user is the leader, by Zero if the user is the only member). Hearts appear around them, and the mage blushes. Afterwards the other character disappears in a puff of smoke and the mage stands up from the ground.

Other media
The core appeared in the Rockman X4 manga, flying near Iris and assisting by firing lasers. Zero smashed it with his fist and later pulled Iris out of the Ride Armor-like body. In the manga it appears to be only a support mechanism, as Iris does not return to normal after its destruction.