Secondary skill
Secondary skills are beneficial qualities of heroes. There are 28 different secondary skills and each one has three levels: basic, advanced and expert. Each level increases the capability of the secondary skill making it more influential. Typically in custom scenarios heroes start with either two secondary skills at basic level or one at advanced level. Each hero can have up to eight secondary skills.
Secondary skills can be divided into three categories: combat skills, magic skills and adventure skills. Combat skills affect directly to combat capabilities of creatures under hero's command; magic skills affect hero's abilities to cast spells; and adventure skills improves hero's adventure map qualities.
Once secondary skill is learned, it cannot be removed. As a result, secondary skill choices on level-ups are among the most important decisions in the game.
Secondary skill advancement rules
If a hero does not already possess eight secondary skills, he/she gets an offer of two different skill during level-up. The first offer is a skill s/he already has but which is not yet at expert level. The second offer is random, but the probabilities of the skills offered are dependent on the hero's class. If a hero already has all secondary skills at expert level, both offers are random. If a hero already has eight secondary skills, both offers are random but within the skills pool this hero is allowed to have.
There are few other ways to acquire a secondary skill. They can be learned from scholars, witch huts or universities on the adventure map. In Armageddon's Blade Conflux has a special building magic university that can teach any number of the four schools of magic. Additionally, at map editor it is possible to set events on the map, that teaches secondary skills.
The random seed for offering skills is separate for every hero and is fixed at start of the scenario, not excluding for heroes not yet hired by any player; therefore, even when reloading, or hiring, re-hiring and levelling your heroes in different order, they still will be offered the same sequence of skills upon reaching the next level. The only option to change these is when receiving another secondary skill, e.g. from Witch Hut or Scholar. Every choice affects future upgrade options, so upon replaying the same saved game the alteration of choices may actually lead to the entirely different final combination of skills.
Heroes are also guaranteed to be offered Wisdom or school of magic every few levels: Wisdom will be offered at level 6 for Might heroes, and at level 3 for Magic heroes if it was not offered before. It will be offered again from whenever it was offered at most 6 levels later for Might heroes, and at most 3 levels later for Magic heroes. The same applies to one of the schools of magic every 4 levels for Might heroes and every 3 levels for Magic heroes. The only exception is the Elementalist class, which uses the same counter as Might heroes. In HotA 
numbers for Elementalist class were changed to match the numbers for Magic heroes.
The algorithm can be summed as following:
- Create two categories of skills: The ones hero has at the Basic/Advanced level, and the ones the hero has not learned yet. Ignore Expert level skills and globally banned skills (e.g. Navigation).
- If one of the categories is empty, offer two skills from the other category; if there is only one skill to offer, it will be forcefully added to the hero; if there is none, level-up with gaining only primary skill.
- If the hero is guaranteed to get offered Wisdom or School of Magic, do as such. This applies to both slots (left and right skill). Wisdom has always priority, the Schools of Magic are resolved based on the relative probabilities (see 4.)
- For each slot, if the skill is not guaranteed to the rule above, select the skill based on the weighed probability, according to the hero class. If the hero's class is banned from obtaining a specific skill but the hero has it, consider the weight to be equal to 1.
- If a Wisdom or School of Magic was offered (either by chance or by force), reset the respective counter.
- Heroes starting at higher level than 1, e.g. in Prison, are considered to have always picked the left skill, so they will prioritize upgrading to learning new skills.
Frequency Across All Hero Classes
The following chart is a chart for all hero classes and what skills are the most and least common in the game; the percentage represents roughly the frequency a skill is offered. Calculating the average frequency at which a skill is offered in a category is simple; each hero has probabilities to be offered a skill in increments of 1/112. Taking Necromancy as a simple example, all heroes except for Necropolis heroes have a 0/112 chance of being offered it; while both Necropolis hero classes have a 10/112 chance of being offered it (if not starting with it). This would bring the sum of lots to 20. Given that there are 18 hero classes, 18 x 112 = 2016 lots in total calculation. Thus, we can divide 20 by 2016 to get the frequency the skill is offered among all hero classes, which is roughly 0.99%, making it the rarest naturally offered skill in the game.
| # |
|---|
| 1 |
| 2 |
| 3 |
| 4 |
| 5 |
| 6 |
| 7 |
| 8 |
| 9 |
| 10 |
| 11 |
| 12 |
| 13 |
| 14 |
| 15 |
| 16 |
| 17 |
| 18 |
| 19 |
| 20 |
| 21 |
| 22 |
| 23 |
| 24 |
| 25 |
| 26 |
| 27 |
| 28 |
| Secondary skill | All Classes |
Might Classes |
Magic Classes |
Good Classes |
Neutral Classes |
Evil Classes |
|---|---|---|---|---|---|---|
 Air Magic |
2.5 | 2.0 | 3.0 | 3.0 | 2.7 | 1.9 |
 Archery |
4.2 | 5.2 | 2.7 | 4.2 | 4.6 | 3.7 |
 Armorer |
4.1 | 5.9 | 2.3 | 4.2 | 4.5 | 3.7 |
 Artillery |
3.7 | 5.0 | 1.8 | 2.8 | 4.5 | 3.9 |
 Ballistics |
5.4 | 6.2 | 4.7 | 4.5 | 6.1 | 5.7 |
 Diplomacy |
2.9 | 2.4 | 3.5 | 3.9 | 1.9 | 3.0 |
 Eagle Eye |
4.2 | 2.9 | 6.3 | 4.2 | 4.2 | 4.2 |
 Earth Magic |
3.3 | 2.7 | 3.9 | 2.7 | 3.1 | 4.0 |
 Estates |
2.5 | 2.3 | 2.6 | 3.4 | 1.6 | 2.5 |
 Fire Magic |
2.1 | 1.4 | 2.9 | 1.0 | 2.5 | 2.8 |
 First Aid |
3.4 | 2.5 | 5.1 | 4.6 | 3.6 | 2.1 |
 Intelligence |
4.0 | 2.4 | 6.3 | 4.5 | 3.4 | 4.2 |
 Leadership |
3.2 | 4.1 | 2.1 | 4.0 | 3.1 | 2.4 |
 Learning |
4.1 | 4.2 | 3.6 | 4.5 | 4.2 | 3.6 |
 Logistics |
4.8 | 5.7 | 3.4 | 4.0 | 5.5 | 4.8 |
 Luck |
2.6 | 2.4 | 3.1 | 4.3 | 2.2 | 1.3 |
 Mysticism |
4.4 | 3.1 | 6.2 | 4.0 | 4.2 | 4.9 |
 Navigation |
3.7 | 4.6 | 2.9 | 3.3 | 3.7 | 4.0 |
 Necromancy |
1.0 | 1.0 | 1.0 | 0.0 | 0.0 | 3.0 |
 Offense |
4.5 | 5.8 | 2.5 | 3.6 | 5.2 | 4.6 |
 Pathfinding |
3.9 | 4.6 | 2.9 | 3.6 | 4.5 | 3.7 |
 Resistance |
3.0 | 4.7 | 1.1 | 3.3 | 2.5 | 3.1 |
 Scholar |
3.7 | 1.9 | 6.1 | 4.2 | 3.3 | 3.6 |
 Scouting |
3.6 | 4.6 | 2.2 | 3.3 | 4.3 | 3.1 |
 Sorcery |
4.0 | 2.5 | 6.3 | 3.7 | 3.7 | 4.6 |
 Tactics |
3.8 | 5.2 | 1.8 | 3.0 | 4.3 | 4.2 |
 Water Magic |
2.3 | 1.8 | 3.0 | 3.0 | 2.4 | 1.6 |
 Wisdom |
5.2 | 3.7 | 7.2 | 5.5 | 4.2 | 5.8 |
In Horn of the Abyss, the calculations are trickier, as each hero class does not have an exact 112 lots of skills, but rather each hero class has 112 to 121 lots of all skills. Things are further complicated by Resistance being banned by default on all maps and templates and consequently the vast majority of games played not having it in the lots. Furthermore, Navigation is also banned by default on all random map templates without water (and the vast majority of templates were created with the "None" water setting in mind, as with water, border guards and other barriers can often be bypassed). Removing both Navigation and Resistance from the lots make the lots range from 102 to 111.
In this chart, the sum of each column will be over 100%, as Navigation and Resistance are not counted, and their listed percentages are not their true percentages, but are there only to compare to other skills.
An example calculation: on average, each hero class has 107 lots if Resistance and Navigation are both disabled. There are currently (as of 1.6.1) 20 hero classes in Horn of the Abyss, which makes the grand sum of lots 107 x 20 = 2140. Interference has 54 lots across all hero classes, making its percent 54 / 2140 ≈ 2.52%. Resistance has 68 lots across all hero classes, making its percent 68 / 2140 ≈ 3.18%; but this is only a comparative value, rather than a true percentage, as the chance to get Resistance if it is disabled is 0. A real value could be computed if Resistance was enabled and Interference disabled, or if both were enabled; however enabling or disabling any skill will change the grand sum and thus change the percentages of all skills. For example, if all skills are enabled, the grand sum becomes 2294. Interference's average chances becomes 54 / 2294 ≈ 2.35%; while Resistance's average chances becomes 68 / 2294 ≈ 2.96%; while Artillery's chances go from roughly 4.63% to 4.32%.
The chart below assumes Resistance and Navigation are both disabled and the figures given for those skills are only for comparison rather than true percentages.
| # |
|---|
| 1 |
| 2 |
| 3 |
| 4 |
| 5 |
| 6 |
| 7 |
| 8 |
| 9 |
| 10 |
| 11 |
| 12 |
| 13 |
| 14 |
| 15 |
| 16 |
| 17 |
| 18 |
| 19 |
| 20 |
| 21 |
| 22 |
| 23 |
| 24 |
| 25 |
| 26 |
| 27 |
| 28 |
| 29 |
| Secondary skill | All Classes |
Might Classes |
Magic Classes |
Good Classes |
Neutral Classes |
Evil Classes |
|---|---|---|---|---|---|---|
| Air Magic |
2.8 | 2.1 | 3.5 | 3.1 | 3.2 | 2.0 |
| Archery |
4.6 | 6.2 | 3.1 | 4.3 | 5.4 | 3.9 |
| Armorer |
4.0 | 5.8 | 2.2 | 4.3 | 3.9 | 3.9 |
| Artillery |
3.8 | 5.8 | 1.8 | 2.9 | 4.2 | 4.1 |
| Ballistics |
5.4 | 6.3 | 4.6 | 4.6 | 5.6 | 5.9 |
| Diplomacy |
3.1 | 2.7 | 3.5 | 4.0 | 2.3 | 3.1 |
| Eagle Eye |
4.2 | 2.3 | 6.1 | 4.3 | 4.0 | 4.4 |
| Earth Magic |
3.5 | 2.9 | 4.1 | 2.8 | 3.5 | 4.2 |
| Estates |
2.7 | 2.7 | 2.6 | 3.6 | 2.0 | 2.7 |
| Fire Magic |
2.2 | 1.5 | 2.9 | 1.1 | 2.5 | 3.0 |
| First Aid |
3.5 | 1.9 | 5.1 | 4.8 | 3.5 | 2.2 |
| Intelligence |
4.3 | 2.0 | 6.6 | 4.6 | 4.0 | 4.4 |
 Interference |
2.5 | 4.9 | 0.2 | 2.9 | 2.1 | 2.7 |
| Leadership |
3.4 | 4.6 | 2.1 | 4.2 | 3.4 | 2.5 |
| Learning |
4.1 | 4.5 | 3.7 | 4.6 | 4.0 | 3.7 |
| Logistics |
4.9 | 6.4 | 3.5 | 4.2 | 5.4 | 5.0 |
| Luck |
3.0 | 2.7 | 3.3 | 4.5 | 3.1 | 1.4 |
| Mysticism |
4.3 | 2.5 | 6.1 | 4.2 | 3.8 | 5.1 |
| Navigation |
4.0 | 4.8 | 3.3 | 3.4 | 4.3 | 4.2 |
| Necromancy |
0.9 | 0.9 | 0.9 | 0.0 | 0.0 | 3.1 |
| Offense |
4.8 | 6.9 | 2.7 | 3.7 | 5.6 | 4.8 |
| Pathfinding |
4.3 | 5.4 | 3.3 | 3.7 | 5.2 | 3.9 |
| Resistance |
3.2 | 4.9 | 1.5 | 3.4 | 2.9 | 3.3 |
| Scholar |
3.7 | 1.3 | 6.2 | 4.3 | 3.3 | 3.7 |
| Scouting |
3.6 | 5.1 | 2.2 | 3.4 | 4.1 | 3.3 |
| Sorcery |
4.2 | 1.9 | 6.4 | 3.9 | 3.9 | 4.8 |
| Tactics |
4.1 | 6.1 | 2.1 | 3.1 | 4.6 | 4.4 |
| Water Magic |
2.7 | 1.8 | 3.6 | 3.1 | 3.2 | 1.7 |
| Wisdom |
5.3 | 3.0 | 7.6 | 5.7 | 4.3 | 6.1 |