There are 3 ways to upgrade a Survivor

1. Survivor Level Up

Level up by earning EXP through killing zombies.

For every 25 level increase of the Survivor, the Survivor's ATK doubles, and depending on the rank of the Survivor, other Survivors' increase by 50 - 100%.

The power of headshots increases for every 100 levels of the Survivor.

2. Weapon Level Up

Level up with Parts acquired from exploring or from 'Game Over'.

ATK increases dramatically after leveling up. For every 25 levels of the Survivor, ATK doubles.

3. Promotion

Use Badges and combat items to upgrade Survivor ranks.

Bonus gained by ranks are as follows.

★★
ATK increase by 100% + 1 additional item slot + Skill power increase by 3 times + Food/Water consumption reduction by 10% + Survivor max level increase

★★★
ATK increase by 100% + 1 additional life (Survive zombie attack once) + Parts acquired amount increase by 100% + Food/Water consumption reduction by 10% + Survivor max level increase

★★★★
ATK increase by 100% + 1 additional item slot + Parts acquired amount increase by 100% + Food/Water consumption reduction by 10% + Survivor max level increase

★★★★★
ATK increase by 100% + 1 additional life (Survive zombie attack once) + Parts acquired amount increase by 100% + Food/Water consumption reduction by 10% + Survivor max level increase

Badges can be acquired from Danger zones from exploration, as well as from 'annihilating' zombies. Combat items can be acquired from exploration or through purchases from the Shop.