So I'm trying to understand how skill points work.
I understand that they determine how much mana I can use in a fight and how many turns I use to cast a spell, but keeping the red staff at zero I have no problem casting spells.
Now I have 25 SP with the red staff at zero, why?
If I want more SP I should move the staff more than 25?

skill goes into raising your casting skill which is how much mana you can use within each fight
as well as how much can be used per turn casting while Overland (the main map screen)

if i recall correctly to raise it you need to cumulatively build up SP equal to double the current casting skill level

as you adjust the staffs its takes/gives to the other 2 equally (unless you lock a given staff
by clicking the jewel on top of that staff)
so i guess you were adjusting another staff without noticing the effect on the skill staff

note: the SP shown is only how much you are currently putting in this turn,
i dont think there is a way to see how much is pooled towards the next casting level

Yeah the red staff is a basically a turn-by-turn investment in improving your casting skill: if you max it out it does not instantly increase your ability that turn, nor does it remove your skill if you zero it. Instead, when you hit Next Turn the points are added to your cumulative total, from which casting skill is derived.

To improve your casting skill by 1, you need to invest 2x your current casting skill worth of power.

Other things adding full skill points: spellbooks picked at start +2/ea, Archmage +10

There's also this excessively long explanation of the casting skill mechanics if you want more specifics

Now I have 25(25) casting skill and the red staff i set at 0SP (from many turns), so to improve my casting skill I should set the staff at least to 50SP right?

Another thing, why I have 25 casting skill? I have 10 spellbook (9+1) and warlord

Each turn you get a number of power points, and those power points are distributed to the three wands each turn. Power comes from things like nodes, citizens of certain races, and religious buildings (ex. shrine).

The first wand is Mana. Any spell maintenance you need to pay is deducted from your mana income first, then any remainder after that calculation is applied to your mana stockpile (if you have more mana income than maintenance costs, the extra is added to your mana stockpile).

The second wand is Research. This is the number of research points that is being applied toward your current research target. Libraries and similar buildings will add to this total as well. Any overflow beyond what is needed to finish the current spell is lost, so you can see some savings by monitoring your progress and not overspending on that last turn.

The third wand is Skill. Power spent on this wand affects how fast your spell skill grows. You need to spend a number of points on this wand equal to 2x your current casting skill in order to gain a new point of casting skill. Any power spent on this wand is not lost; if it takes you several turns to spend the necessary power, that's fine. If you need to reduce expenditures on Skill for awhile, then do so, but it is useful to keep this as high as you can afford to keep it. Sadly, there is no way to see how much power you've spent on this wand. The +10 spell skill from Archmage is NOT included when calculating how much power you need to spend to raise your spell skill.

Your spell skill is listed below the three wands. Any heroes that are staying in the city with your wizard's tower will add their spell skill to yours for casting spells (with some limits; they don't make spells Instant). This is the value that increases as you spend power points on the Skill wand.

I just want to add that the benefits of a high casting skill apply both to combat and overland spells.

In combat, your current skill is the pool of magic points your wizard has to cast spells with.

· This is not how much mana the spell will actually cost, since you may be penalized by how far away from your fortress the combat is occurring.

· This is also not affected by any magical abilities your heroes and champions might have; magic-wielding heroes have their own mana pools (and spell lists).

· Also, the mana pool resets with each new battle, not at the end of your turn.

Overland, higher magical skill allows you to cast more and more spells instantly, possibly even multiple spells per turn; more powerful spells will also take fewer turns to complete, giving enemies less time to dispel them (if they are so inclined).

So while it does take a long time to develop, once you do have it you're going to find yourself OP beyond belief.

That should be "giving enemies less time to Spell Blast them". Spell Blast happens during casting, Dispeling happens after the spell has been cast (if it is an ongoing enchantment).

Ok guys, we are losing the point.
I understand where the Power Base come from and how is split in Mana, Research and Skill.

My question are:
-First-
I have 9 life book and 1 nature
Only Warlord skill
No hero in the "capital"
No special event

Why I have 25 Casting Skill? I'm keeping my SP to 0.

-Second-

With 25 Casting Skill I should set my SP at least 50 to see an improvement?

That depends on your starting build and what has happened during the game. It appears you found a book in a ruin or node, but that new book doesn't factor into casting skill at all.

I'm going to assume you started with Warlord and 9 spell books (total of 11 picks); the particular colors of the books doesn't matter for this calculation. Your starting casting skill equals your starting number of spell books times two (and then +10 if you started with Archmage, which doesn't apply in this case), so I'm assuming you had 18 casting skill at the very beginning of the game. There is only one way to gain (permanent) casting skill after the game starts, which is to dump Power into the Skill slider, so over the course of the game thus far you've spent at least ((18x2)+(19x2) +(20x2)+(21x2)+(22x2)+(23x2)+(24x2)) = 294 power points on the Skill slider.

There is a way to lose casting skill, which is having Cruel Unminding cast on you, but I'm guessing this hasn't happened.

To increase your casting skill to 26, you'll need to spend at least 50 power points on the Skill wand. They don't all have to be spent in the same turn; power spent on Skill accumulates in a hidden pool, and your casting skill is calculated based on that pool (so if you have enough Power, you can gain multiple casting skill in one turn).

If you never spend any more power on Skill (and if you never have Cruel Unminding cast on you), then you'll have 25 (permanent) casting skill for the rest of the game.

Wait, are you saying that my casting skill can't go down?
If now I put everything in to my red staff for 10 turns and then I switch back to zero I will have (I don't know, let's say...) 32 casting skill?

Pretty sure that isn't what I said. :)

There is one specific spell, Cruel Unminding, that causes the target to lose a small percentage of their spell skill. The AI is almost certainly not going to cast it when they could be summoning ghouls instead, but the spell does exist.

In general though, you can expect your spell skill to either stay the same or increase over the course of the game.

I can't answer that accurately without knowing your Power income, but it sounds like you are getting the idea. Keep in mind that as your spell skill grows, it takes progressively more expenditures on the Skill wand to add a new point. It is still an excellent thing to invest in, though.

Thank you, everything make more sense now!

Great! If you have any more questions, feel free to drop in and ask.