Info[]
The 221 build is a way to determine a fresh face's stats when spawned. There are 5 categories to invest to in the 221 build and as you've guessed: add up to 221. Here's each category and what it does:
Categories[]
HP[]
Determines the general Vitality of the Character. The more HP, the more Vitality.
ATK[]
Affects Strength primarily, but also gives a bit of Dexterity, and Vigor.
MAG[]
Affects mostly Vigor and Intelligence. Feeds slightly into Dexterity, Vitality, and Agility.
DEF[]
The key to gaining Resistance later in the game. Gives slight Strength and Vitality.
SPD[]
The main factor of Agility. Gives a bit of Dexterity as well.