Frost Knight is the freeze specialist among the hidden classes of Lord Nine: Infinite Class (LordNine) — and the one class on this roster with a hard rule about who should play it. The freeze window it creates only rewards magic damage, which makes it the natural hidden class for staff and battle staff builds and a poor fit for everyone else.
Verified current as of the August 12, 2026 update. All skill text below matches the live in-game tooltips, cross-checked against the game data files.
How to Unlock Frost Knight
Hidden classes in LordNine unlock automatically when you carry a specific combination of six abilities at the same time. The combo is arranged as three slots with two interchangeable options each — you need one ability from both columns of every row, active simultaneously on the same character. Order doesn't matter, and the abilities can come from any base class you've leveled.
| Slot | Option A | Option B |
|---|---|---|
| 1 |  Frost Weapon |  Earth Shock |
| 2 |  Cutting Strike |  Life Tap |
| 3 |  Leech |  Anatomy |
Swapping any qualifying ability out of your active build reverts the class until the combo lines up again — plan swaps carefully. For every other combo in the game, see the complete hidden class combination reference.
The Class Skill: Frost Curse
Class Skill: Deals Combined Damage to the target and inflicts Frozen for 4 sec with a +60% chance. When Frozen ends, reduces Movement Speed for 10 sec. Reduces Movement Speed around the target for 10 sec. (Up to 5 targets)
Here's the mechanic that defines the class: while a target is Frozen, only magic damage connects — physical damage doesn't go through the freeze at all. A staff or battle staff user free-casts into a frozen target; a melee or physical ranged build watches its damage bounce off its own crowd control. That single interaction is why Frost Knight is a magic-DPS class in practice, whatever the combo table might suggest.
Who Should Play It
Staff and Battle Staff are the only two weapon classes that use Frost Knight effectively. The milestone spread backs the same story — Critical Hit and Critical Hit Damage at 500 feed burst casting, and the freeze gives you free windows to land it.
It performs in both PvE and PvP, and the PvE side gets a real step up at ability level 800 when Blizzard comes online.
Blizzard at Ability Level 800
Blizzard drops a 7-meter Ice Storm on the target for 10 seconds — 50% bonus Magic Damage every second, plus a Movement Speed slow that stacks up to three times on anything that stays inside. If you've played Dota 2, the feel is close to Crystal Maiden's Freezing Field: a zone you commit to and everything inside melts. It's the main reason Frost Knight's PvE ceiling rises at 800.
Build: Weapons, Stats, and Relics
Weapon: staff or battle staff, no serious alternative.
Relic priority: Origin of Destruction (Attack) first, then Magic Storm (Skill Damage) — your kit is skill-driven — then Barrier of Protection (Defense), with Crystal of Life (HP) last. Budget the upgrade path with the relic calculator.
Ability Total Level Bonuses
| Ability Total Level | Bonus |
|---|---|
| 100 | Endurance Ignore +50 |
| 200 | Movement Speed +8% |
| 300 | Attack Speed +8% |
| 400 | Attack Power +70 |
| 500 | Critical Hit +100, Critical Hit Damage +7% |
| 600 | When HP is at 50% or below, increases the caster's Endurance. |
| 700 | Attack Power +100 |
| 800 | Blizzard — Creates an Ice Storm in a 7m radius around the target for 10 sec, dealing an extra 50% Magic Damage per second and reducing Movement Speed by 20% for 3 sec, stacking up to 3 times. |
Your ability total level is the sum of every ability level on your build, so any ability you level walks you up the ladder. Milestones 100–500 come fairly quickly — the game hands out Expert and Maestro scrolls often. At 600 the wall starts: promoting an ability tag from level 90 to 100 takes a Master Scroll, crafted from 10 Maestro Scrolls, and you need six of them. 700 and 800 are long-haul goals if you rely on freebies and grinding alone — the 800 milestone effectively asks for four ability tags at level 140 and two at 120, where 100→120 costs one Master Scroll and 120→140 costs two more.
Verdict
For magic builds, Frost Knight is the clear hidden-class pick and holds a solid mid-table spot overall — on par with Sword Master and Trinity in the current pecking order, below Destroyer and Immortal Knight. For physical builds it's a trap: the freeze that defines the class actively blocks your damage.
Where Next?
- The complete hidden class combination reference — every slot for all eight classes
- Free LordNine tools — relic upgrade costs with live market prices, enhancement odds, MP sustain math, and homun probabilities
