Double Soul (MMBN4)

Double Soul (ソウルユニゾン Soul Unison) is the main transformation of Mega Man Battle Network 4. To Double Soul, the player must sacrifice the respective element chip to unite with MegaMan. The transformation will last 3 turns or until it is overwritten by another Soul. However, there are Mod Cards that will allow MegaMan to remain in a Soul permanently.

Red Sun

Guts Soul
Sacrifice	Crack Chip
Power Attack	Guts Punch (60 damage) Non-flashing. Small pushes.
Abilities	All Null and Crack chips gain +30 damage. Guts Machine Gun: Rapidly pressing B will make MegaMan temporarily invincible and execute a rapid fire attack. (10 damage, up to 5 times)
Fire Soul
Sacrifice	Fire Chip
Power Attack	Flamethrower (50 damage) Fire attack.
Abilities	Fire Body: MegaMan can walk on Lava panels and is weak to Aqua attacks. Stepping on Lava Panel will have MegaMan heal 50 HP. Upon Unison, the stage is reset into one with plus-shaped Grass Panels. Charge Fire Chip: The chip becomes a Fire Arm that travels down the whole row. (Chip ATK + 50 damage)
Roll Soul
Sacrifice	Recovery Chip
Power Attack	Roll Arrow (30 damage) The struck target's BattleChips are destroyed.
Abilities	MegaMan heals 10% of his HP anytime he uses a BattleChip.
Wind Soul
Sacrifice	Wind Chip
Power Attack	Wind Racket (50 damage) Non-flashing. Big Push.
Abilities	*B Button: MegaMan's normal buster becomes Air Shot. Air Shoes: MegaMan can walk over Broken panels. Float Shoes: MegaMan ignores Cracked, Ice, Lava, and Sand panels. Upon Unison, NorthWind takes effect. The enemy's Barrier or Aura are blown away. For 3 turns, a Fan effect is active on the enemy's field.
Thunder Soul
Sacrifice	Elec Chip
Power Attack	Zap Ring (20 damage) Elec attack. Paralyzes.
Abilities	Elec Body: MegaMan is weak to Wood attacks. All Null and Elec chips will paralyze.
Search Soul
Sacrifice	Invisible Chip
Power Attack	Scope Gun (10 damage x5) Invis-piercing.
Abilities	Upon Unison, all invisible enemies are no longer flashing. A Shuffle button appears on the Custom Screen that can shuffle non-selected chips with the Folder. This can be used up to 3 times per turn.

Extra Notes

• Fire Soul's unison ability resets all other Panel types on the field. It can be used to clear any unfavorable stages.
• Wind Soul's Fan effect can be overwritten by a Wind or Fan chip. If that obstacle is destroyed, there will be no Fan effect on the field.
• Thunder Soul's paralyzation applies to all hits of a multi hitting chip. With the exception of ElemSand, which will eventually cause flashing.

Blue Moon

Aqua Soul
Sacrifice	Aqua Chip
Power Attack	Bubbler (20 damage) Aqua attack, charges very quickly.
Abilities	Aqua Body: MegaMan won't slip on Ice panels and is weak to Elec attacks. Charge non-dimming Aqua Chip: x2 damage.
Number Soul
Sacrifice	Plus Chip
Power Attack	Number Die (10 damage x Die Roll) If the Die hits the enemy directly, it will only do 10 damage.
Abilities	All Null chips gain +10 damage. The Custom Screen displays 10 chips to select from.
Wood Soul
Sacrifice	Wood Chip
Power Attack	Twister (20 damage, up to x8) Wood attack, non-flashing.
Abilities	Wood Body: MegaMan will rapidly heal on panels and is weak to Fire attacks. Status Guard: MegaMan can't be paralyzed, blinded, confused, or immobilized. If a selected non-dimming Wood chip is followed by a Null Chip, the Wood chip consumes the Null Chip and its attack power is added to it.
Metal Soul
Sacrifice	Break Chip
Power Attack	Metal Fist (150 damage) Breaking.
Abilities	Break Buster: The normal buster will guard-pierce. Charge non-dimming Null or Break Chip: 2x damage.
Junk Soul
Sacrifice	Summon Chip
Power Attack	Poltergeist (100 damage per obstacle) All obstacles thrown will be breaking.
Abilities	Upon Unison, all invisible enemies are no longer flashing and all enemies have confused status. Two recycled "Junk-Chips" appear in the Custom Screen every turn. The chips can be either from you or your opponent's.
Proto Soul
Sacrifice	Sword Chip
Power Attack	Wide Sword (80 damage) Non-flashing. Unlike most busters, this attack can counter hit.
Abilities	All Sword attacks will not cause flashing. B + Left: Reflect. If an attack is blocked, 100 damage is sent down the row. Charge non-dimming Sword Chip: x2 the damage of the Sword Chip and MegaMan steps 2 steps forward while using it. Z Saver and Slasher BattleChips can be charged for x2 damage but MegaMan will not step forward.

Extra Notes

• ElemIce, ElemLeaf, and ElemSand can hit up to 5 times on enemies that don't go into flashing. The damage can be further boosted by Aqua, Number, and Metal Souls' abilities.
• One of strongest Null chip target for Wood Soul's ability is Blue Moon. Through the Select Battle feature in Network, its attack power can be raised to 600. Some Wood Chips also have the potential to hit multiple times.
• Proto Soul's charging for unconventional Sword Chips will require more work. For VarSword and Z Saver commands, the A Button must be pressed down again after releasing it for the charge.
• During ToyRobo's ShadeMan fight, the mandatory DarkSword can be used to Double Soul into Proto Soul and can be charged up.