Amalgamation
Amalgamation is basically merging 2 or more units to form a totally different unit.
Here is a list of the combinations that have been discovered:
Enchanter (N) + Mechanic (N) = Android (R)
Fox Spirit (R) + Onmyoji (N) = Oni (R)
Arachne (R) + Lamia (N) = Medusa (R)
Cleric (N) + Priest (N) = Bishop (N)
Summoner (N) + Wizard (N) = Sage (N)
Pixie (N) + Witch (N) = Little Witch (N)
Dryad (N) + Archer (N) = Elementalist (N)
Bugbear (N) + Elf (N) = Dwarf (N)
Thief (N) + Adventurer (N) = Treasure Hunter (N)
Harpy (N) + Bard (N) = Siren (N)
Lycaon (N) + Barbarian (N) = Berserker (N)
Musician (R) + Siren (N) = Diva (R)
Europa (R) + Selene (R) = Anubis (R)
Ladybird (R) + Alraune (R) = Fungus (R)
Soldier (R) + Scientist (R) = Grenadier (R)
Metal Slime (R) + Gold Girl (N) = Medal Girl (R)
Ghost (R) + Kung-Fu Master (R) + Phantom (N) = Jiang Shi (R)
Sylph (R) + Undine (R) + Salamander (R) + Gnome (N) = Lightning (R)
Daphne (HR) + Dione (HR) + Rhea (HR) + Calypso (HR) = Gaia (SR)