General questions

[snakesoul]

Hi,

I'm new and I have some questions for you guys:

- At some levels, the game asks me if I want to increase str, int or dex, but most of level up times it doesn't ask me.

- I have a spell which failure rate is 99%, how can I decrease it? It's invisibility.

Thanks!

[Siegurt]

- At some levels, the game asks me if I want to increase str, int or dex, but most of level up times it doesn't ask me.

This happens at experience levels divisible by 3, so at XL 3,6,9,12,15,18,21,24,27 (A total of 9 times maximum)
Some races also get a bump to a random stat at different intervals, for example humans get a bonus to one of Str, Dex or Int every 5 levels. (And at level 15 they would get a random bump and one which you would be prompted about.)

I have a spell which failure rate is 99%, how can I decrease it? It's invisibility.

There are a pretty large number of factors which reduce spell failure:
Intelligence
Spellcasting
Relevant spell schools (for invisibility that's "Hexes")
Armour penalties (Heavier armour penalizes you spell success rate, somewhat reduced penalties are applied if you have higher strength)
Shield penalties (Larger shields require more shield skill to eliminate said penalties)

[reaver]

Relevant spell schools (for invisibility that's "Hexes")

Since getting rid of heavy armor penalties just means not wearing it, this is the one you're going to care about 95% of the time.

If you don't know what skills are, hit "m" and "/" to choose which ones to train as you kill monsters. The default is for the game to automatically choose which skills to train based on what you do ("Auto" mode), which normally allocates your XP worse than if you do it.

Have you played the tutorial/Hints Mode yet? You've probably got most of the things they teach down if you're getting deep enough to memorize invisibility, but they cover quite a bit of material that you may find helpful.