
Originally Posted by
Arreat's
Skill Points from Items
Staves, Wands, Scepters and Class-specific items give from 1 to 3 extra skill points. You will receive the skill points only when you have the item or weapon equipped. These items will allow you to use skills that you have researched or spent a skill point. These bonus skill points do not allow you to advance down the skill tree unless you already have a point in that skill. So an item that gives +1 to Teeth for the Necromancer does not enable you to place one point into Corpse Explosion at level 6 until you put at least one point into Teeth.
Some Items give +1 to +2 to all class Skills. These items will only add skill points to those skills, which you already have at least one skill point. You cannot use these items to unlock all of your skills.
Some Unique and Set Items give +1 to +2 to all skills (not class specific). These items will also only give additional skill points to those skills that you already have at least one skill point.
Some Items give +1 to +3 to all Skill Tab Skills such as +1 to all Combat Skills (Paladin), or +3 to all Curses (Necromancer Curses). These items will only give +1 to +3 skill points in skills in that specific Skill Tab. These items will also only give additional skill points to those skills which you already have at least one skill point. These items will not allow character classes use these skills if they don't normally have these skills available.
Skill Points that work for Any Class ("oskill" Skill Points)
The Trang-Oul's Avatar Set gives +18 to Fireball and +13 to Fire Wall. The boost to fireball (as well as Frostwind's arctic blast bonus and a whole lot of other items) are examples of what's internally known as an "oskill". These are skill bonuses that work for any class. If a Necromancer is wearing a Trang-Oul set, he'll get +18 fireball and any +X To All Skills equipment can further increase this. The same applies to all other non-sorceress class wearing a part of that set.
However, oskills work differently for classes that "own" that skill. In this case, it's a Sorceress getting a bonus to Fireball. In the other case, it was a Druid getting a bonus to Arctic Blast. If a character gets an oskill bonus to a skill that class "owns," the bonus is restricted to a maximum of +3. If a Barbarian is dual-wielding Call to Arms runeword weapons, the +3 cap is applied to the total from both weapons. This is all intentional, in order to balance these items.