Berzerker Challenge Guide

From the in-game description:

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Requirement
To attempt the Berzerker Challenge, you'll need to be at least Level 120.

Rings
Upon completing the Berzerker Challenge, Nameless rewards you a Magic Stone, which can be used to either create or upgrade a Berzerker Ring. Yun at Ninja Castle can do this for you.

Berzerker Ring (Level 1)

• Costs 1 Magic Stone of Humility (attained from fighting an Easy Mode Ergoth) and 2m mesos to create.
• Two random stats are chosen and allocated to this ring (STR / DEX, STR / INT, STR / LUK are some possible combinations).
• The stat range for both stats is 1 ~ 3. The best possible Berzerker Ring (Level 1) is +3 / +3.

Upgrade to Berzerker Ring (Level 2)

• The upgrade costs 1 Magic Stone of Honesty (attained from fighting a Normal Mode Ergoth), a Berzerker Ring (Level 1) and 1m mesos to upgrade.
  • Upgrading has a 20% rate of success. All materials except the Berzerker Ring (Level 1) is expended on failure.
• Depends on the original Level 1 ring stats, adding anywhere from 2 ~ 4 per stat. The best possible Berzerker Ring (Level 2) is +7 / +7.

Upgrade to Berzerker Ring (Level 3)

• The upgrade costs 1 Magic Stone of Trust (attained from fighting a Hard Mode Ergoth), a Berzerker Ring (Level 2) and 5m mesos to upgrade.
  • Upgrading has a 20% rate of success. All materials except the Berzerker Ring (Level 2) is expended on failure.
• Depends on the original Level 2 ring stats, adding anywhere from 2 ~ 4 per stat. The best possible Berzerker Ring (Level 3) is +11 / +11.

Modes
Ergoth has 30 different modes, spanning across three difficulty settings. As you unlock higher level Berzerker Rings, Ergoth becomes more difficult. As a result, Ergoth may have anywhere from 2.8m HP (the easiest Easy Mode boss) and 116m HP (the hardest Hard Mode boss).

After Berzerker Ring (Level 3)
Upon earning the Berzerker Ring (Level 3), players will unlock a new tier of prizes. Fighting Ergoth on a daily basis will hand out White Scrolls and a variety of 10% Weapon / Magic attack scrolls.

 

@painfist, that's correct.