Race Shift (種族シフト, Shuzoku shifuto) is a mechanic in Shin Megami Tensei: Nine.
Details
Most demons have hidden attributes known as Species values, ranging from 0 to 100. If the value associated with their own Species is lower than that of others, a Race Shift can be performed at the Cathedral of Shadows, changing that demon into another one of a different Race. If all other values are at least 80, the result will be a Fiend.[1] This is the only way to obtain Fiends legitimately.
Species values can be changed by defeating enemies. When an enemy demon is defeated, demons with the same species will have their associated values decreased, while others have their values increased. Both Species values and eligibility for Race Shifting can be inherited in fusion.[1]
Elements, Spirits, Fouls, and Fiends lack a Species, and thus cannot be used for Race Shifting.