Sorry about the unclearness of the Dark Pikmin; I'll try again (if this doesn't help, just look up Drow elves from Dungeons and Dragons; that's what I'm modeling them after.)
Categories of Abilities of Dark Pikmin: melee (basic), melee (advanced), magic (basic), magic (advanced), other.
Detailed explanation:
Melee (basic):
Open to: Foot Soldiers, Priestesses, Fighters
Entails: incredible stealth and agility in and out of battle.
Melee (advanced):
Open to: Fighters
Entails: amazing hand-to-hand combat, perfect accuracy with thrown or shot (like from a gun) projectiles.
Magic (basic):
Open to: Mages, Priestesses, Fighters:
Entails: Levitation, Faerie fire (harmless fire that can outline a target, making it easier to hit), globes of darkness.
Magic (advanced):
Open to: Priestesses
General prowess in offensive, defensive, and healing magic (fireballs, lightning bolts, temporary enchanting of weapons, the like)
Other:
Open to: all
Entails: precise infrared vision, general ability to navigate in the complete absence of visible light (by hearing, touch, and even smell in rare cases).
Jarlaxle himself can use both advanced magic and melee.