Magichange

Magichange is a feature introduced in Disgaea 3: Absence of Justice (retroactively added into Disgaea 2: Dark Hero Days, which allows Monster units to turn into a Humanoid weapon temporarily. It does not appear in Disgaea D2: A Brighter Darkness, in which a similar system, Monster Mounting, appears, and in Disgaea 6: Defiance of Destiny, where there is no replacement feature.

How it works
Magichange is one of the basic commands Monster units can select, upon which they must target an adjacent Humanoid ally. The Monster will then turn into a weapon with 30% of their unequipped stats, replacing the Humanoid's weapon while the effect lasts. The wielder of the weapon also gains the Monster's Unique Evility(passive skill in Disgaea 2), and the ability to use the Monster's Magichange Skills. Once the effect is over, the Monster becomes unusable for the rest of the battle and the Humanoid goes back to their equipped weapon.

An important feature of Magichange is that all of the EXP/Mana earned by the Humanoid will also be earned by the Monster(or Monsters, for the variants that involve more than one) rather than being split, making it a good way of raising multiple units at once. In contrast, the most notable downside of Magichange is that if the Humanoid dies, all the involved Monsters will also die.

Below is a list of game-specific differences and general boosts.

Disgaea 2

 * Only available in the Dark Hero Days rerelease. It's unlocked in Axel Mode, and can only be used in the main story by starting a new cycle from there.
 * Magichange lasts 2 turns, and an Assembly Bill increases it by 1(must be passed on each Monster separately).
 * If the Monster has a Magichange Scroll equipped, the Magichange weapon will keep a percentage of the original weapon's stats.
 * If a Magichange Weight is equipped, the Monster's highest stat will be copied into the Magichange weapon's attacking stats.

Disgaea 3

 * Magichange lasts 2 turns(3 turns in Absence of Detention) and can only be done if the Monster and Humanoid are in the same Club.
 * The Magintology Club boosts the stats of the weapon and increases the duration by 1 turn.
 * The Shura Support Group decreases its duration by 1 but makes it so the Magichange weapon also uses part of the Humanoid's weapon.
 * The Magichange Lover Specialist increases the percentage of the Monster's stats inherited by the weapon(up to +25%).
 * If a Magichange Weight is equipped, the Monster's highest stat will be copied into the Magichange weapon's attacking stats.

Disgaea 4

 * Magichange lasts 3 turns (6 turns in A Promise Revisited). When it's over, the Monsters will become unusable but the dispatch limit will be recharged.
 * If a stat from the original weapon is higher than the Monster's value, the Magichange weapon will have that amount(increased by 1) instead of the Monster's percentage.
 * Monsters in the Beast Lab (Evil Symbol) will use a percentage of their full stats(rather than the unequipped stats) for the weapon.
 * The Magichange Lover Specialist increases the percentage of the Monster's stats inherited by the weapon(up to +25%).

Disgaea 5

 * Unlike the rest of the series, the stats of the Magichange weapon are equal to 5% of the Monster's unequipped stats plus 100% of the original weapon's stats.
 * Magichange lasts 3 turns. When it's over, the Monster is put back into the Base Panel instead of becoming unusable, though the dispatch limit is not recharged.
 * Monsters can Magichange into the Humanoid's sub weapon. This passes on stats and Evilities, but not Magichange Skills unless the weapon is switched to the main hand.
 * Most Evilities learned from the Ability Squad improve the effects of Magichange.

Magichange 2
A certain Mystery Room in the Item World can give a Monster the ability to use this feature. It allows them to Magichange with a Humanoid that's already holding a Magichange weapon, fusing with it. While this doesn't increase its stats, it does grant the Monster's passive skill and Unique Skills to the wielder. Be warned that activating Magichange 2 reduces the remaining Magichange duration by 1(to a minimum of 1 turn left).

Giant Magichange
A feature available to Monsters in the Fusion Weapon Lab (Evil Symbol). It allows them to use Magichange during Monster Fusion, turning into a giant weapon. A giant weapon not only has increased stats thanks to the fusion, but its Weapon skills and Magichange Skills will have increased range or area of effect.

Dual Magichange
A feature available to monsters in the Dual Dojo (Evil Symbol). It allows them to Magichange with a Humanoid that's already holding a Magichange weapon, replacing the Humanoid's first piece of armor with a second Magichange weapon. This gives the Humanoid the Monster's Unique Evility, and makes it so their attacks/skills execute twice per turn.

Dual and Giant Magichange can be combined, allowing a Humanoid to wield 2 giant weapons and letting you train 5 units at once.

Dual Magichange
A feature available to all Monsters after passing a Bill that's unlocked by performing 10 regular Magichanges. It allows a Monster to Magichange onto a Magichange weapon that's already in use, fusing with it. This will make the weapon giant, add 3% of the Monster's stats into it and grant the Monster's Unique Evility to the wielder. Certain combinations of Monsters will perform a special Dual Magichange, giving the weapon a different sprite and replacing the main Monster's first Magichange Skill for an improved version of it.