Oskills are definitely strange things, which are not to be confused with some skills on pieces of equipment. What constitutes an oskill, and what does not constitute an oskill?
An oskill is defined as an ability to grant skill to a person who is not the original owner of the skill.
"Not the Oskill" Example
Boneshade is an ideal unique wand for Bonemancer. Although other characters, such as Barbarian, can use it as a weapon, it can not give these characters the plus skills of the wand. So the skill - Bone Spirit of Boneshade, which is a Necromancer skill, is not an oskill.
Trang-Oul's Scales is one of the biggest oskill armors in Diablo 2 Resurrected. It gives players who are not Sorceress plus 18 to fireball plus 13 to firewall plus 10 to meteor, and so forth. If players look at their skill bar while wearing this set, they can notice that these skills are actually on their bar, and also, it's a higher level than what it currently stated because oskill can be affected by some items.
An oskill can be affected by some equipment. But it has to be equipment that is suitable and usable for all characters' skills, not a special class.
The Stone of Jordan Ring
These are all skill items that can add points to all skills.
In the case of oskills, other characters can give plus 18 to fireball, but Sorceress can only give plus 3. This is because the fireball is a native Sorceress skill, and the oskill is capped at plus three when she uses it.
It's actually worse than capped at plus three. No matter how many sets of items are used, players can only go up plus three points to a related skill. For example, a Barbarian puts on D2R CTA Flail to get plus three to Cry. However, if he puts on a second one, he still only gets plus three, not plus six. With two Oskill items on, he only gets plus three points to Cry for both Oskill items.
In a word, oskills are restricted at plus three when used by characters who natively own these skills.
Oskills are oddly affected when it comes to specific character builds. So if players want to use the oskill that belongs to the native character, they can choose other characters to put on equipment that has the oskill.
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