Calculator
Skill Book Calculator
One skill, level 1 to 30, costs 11,100 books — and 45% of that sits in the last five levels. Enter where a skill stands and what you're holding.
One skill, level 1 to 30, costs 11,100 books — and 45% of that sits in the last five levels. Enter where a skill stands and what you're holding.
Skill books are the scarcest hero resource after star-ups, and the cost curve is brutal at the top: the final level costs more than taking the same skill from 1 to 15. The question worth asking is rarely "what does max cost" — it is how far do the books I already have actually get me.
| Step | Books | Cumulative | Left in hand |
|---|
Each row is one level. The highlighted row is the last one your books cover — everything below it is what you still have to farm. Costs are identical for gold and purple heroes.
What each level costs and what it has cost you by the time you arrive. Verified for gold and purple heroes; the two are priced identically.
| Step | Books | Total from Lv.1 | Step | Books | Total from Lv.1 |
|---|
Levels 25 to 30 cost 5,020 books — 45% of the entire ladder. Taking a skill from 1 all the way to 15 costs 1,060 — less than the single step from 29 to 30. Any plan that treats "max the skill" as one decision is hiding a cliff in the last five rows.
Which is the argument for spreading books across several heroes' passives rather than maxing one: the marginal book buys far more at level 12 than at level 29.
This page tells you what a level costs. It cannot tell you whether that level is the right place for the book — and the three slots are not close to equal.
| Priority | Slot | Return per book level | Fires |
|---|---|---|---|
| 1st | Passive (slot 3) | ~1% faction buff | Every round, and it multiplies everything else |
| 2nd | Active (slot 1) | ~42 percentage points | Every 10th round — 3–4 casts a battle |
| 3rd | Normal attack (slot 2) | ~4 percentage points | Every round, but from a low base |
A passive book enters the pooled base and multiplies all troop damage for the rest of the battle and every battle after it. An active-skill book is a bigger number that lands three or four times. Normal attack is not a waste — a controlled test in March put it at +0.37% per level, and over a 34-round battle 15 books there beat 15 books on one active skill on raw total damage — but the passive still wins because it compounds through both.
The ladder is an in-game audit of purple and gold hero skill progression (11 September 2026), re-checked against its own total on 14 September. Rows sum to exactly 11,100, which is the verified 1→30 figure. The table on this page is generated from that one source rather than typed twice, so the page and the knowledge base cannot drift apart.
One caveat worth stating: the audit covered purple and gold. Blue and green heroes have not been checked, so treat this as the gold/purple ladder until someone photographs a lower rarity.