Cracked skin is something that isn't seen often in Shengdao and the elders do not look too fondly on the Shijis that are blessed or cursed with this condition. Cracked skin happens in babies when an elder breeds with a common Shiji-Long. Since elders are way more powerful than their descendants, their magic cannot be contained in the smaller form and breaks through their skin.
The magic of those Shiji-Long is always that of the elder and stronger than that of other common Shiji-Long. These cracked Shiji-Long often are unable to control their magic and have outbursts of it, making it dangerous for others and sometimes themselves.
Cracked Shiji-Long are incredibly rare, since the elders in Tianshu have sworn to never mate with their descendants.
For breeding cracked Shiji-Long: They can be bred, but the cracked status is only inherited when two cracked Shijis breed. Vashaa's feathers do not work for this trait.