When you hire a new recruit, you are typically given a one-time free chance to customize them immediately after they join. Steam Workshop::Advanced Character Creation - Basic Steam Community
Since vanilla Kenshi can make characters look "weird" with extreme sliders, many players use mods to improve the base templates. kenshi character presets
Once you’ve adjusted your character's sliders, click the Export button in the customization menu. This saves a .bod2 file. When you hire a new recruit, you are