Skill Scrolls (A.K.A. High Level Skill Scrolls) are items used to unlock level 70+ skills and level 50+ Sorcerer skills that need to be mastered. This is indicated by a red text saying "Skill not yet mastered" when trying to unlock the next level of the skill.
After unlocking the skill you still need to have free skill points to actually get the skill.
When subbing these skills on lower level jobs, the game takes the old level requirement of the skill to calculate the damage and/or duration penalty (Example: level 11 Blood Boil can be unlocked at level 70 with its Skill Scroll, but the penalty used for it is level 73).
To obtain a Skill Scroll, they need to be obtained from either the Item Mall, Northern Turtle Lair, Southern Vermilion Lair, Western Tiger Lair, Trial Tower, or True Trial Tower. Note that scrolls obtained from the Item Mall are not tradeable and that not every scroll can be obtained in-game. For Sorcerer, the first three skill levels that require a Skill Scroll can be dropped as a recipe from many monsters, with the recipes dropped being based on the map. However, the drop rate is extremely low.
Check the Skill List for more information.
- High Level Skill Scroll Information by Leirosa