Skill point

Version 0.18: This article may not be up to date for the latest stable release of Crawl.

Skill points are used to level up skills, rather than direct XP.

General mechanics

When you gain XP, you gain a corresponding number of skill points which are then distributed amongst your active skills. The ratio of skill points to XP changes with the total XP (or, analogously, the total skill points) that your character has ever gained. At the beginning of the game, the ratio will be roughly 1:10, but it will gradually decrease until it hits a cap of 265:10, which will almost always be reached by XL27. This effect is particularly notable when quaffing potions of experience - they give considerably more skill levels early on.

For a given set of skills, the total XP required remains the same, independent of order. If you decide to go for L15 Fighting and L27 Axes, training both skills to L15 or training Axes to L27 first has the same raw XP cost. While the first skill will require less XP, keep in mind that there's also just less XP available earlier on - the reason why this mechanic exists.

Strategy

Absolutely none. The old learndb entry for skill points was "Only galehar [a developer] should know or care what these are." It may not have been the most illuminating, but it is correct in its message: skill points are something the player has no control over, and cannot use to their advantage.

Specific mechanics

The skill point ratio is actually determined by looking at the XL a character with a 130 XP aptitude in the old system (partway between 0 and -1 in the new system) would be at. The skill point costs in XP are as follows:

XP 130 "level"	Skill point cost
1	1
2	2
3	3
4	4
5	5
6	7
7	8
8	9
9	13
10	22
11	37
12	48
13	73
14	98
15	125
16	145
17	170
18	190
19	212
20	225
21	240
22	255
23	260
24-27	265