Phantoma can be harvested from any defeated enemies (excluding the ones that are listed in the “Conditions Where Phantoma is Not Obtained from Defeated Enemies” note). The type of Phantoma obtained is determined as detailed in the chart below, but factors such as enemy type, level, and how the enemy was defeated (finishing blow) affects the Phantoma type. For example, defeating an enemy that possesses the power of fire with a fire-based attack makes it more likely to obtain Red Phantoma from the enemy. For “wild” monsters, the monster type affects not only the type of Phantoma obtained, but the item they drop as well.
Final Fantasy Type-0 HD eGuide Phantoma