The Eidolon's rank determines its stats when summoned to battle. The rank is the sum of the character's Crystarium level and the number of level 5 roles. Thus the maximum rank is 16 (Crystarium level 10 + all roles at level 5).
A cracked tongue may indicate an oral yeast infection, or oral thrush. Oral thrush is caused by the accumulation of the candida fungus in the lining of your mouth. In addition to cracks, symptoms of oral thrush include pain, loss of taste and lesions on the tongue and other areas in the mouth. A weak immune system, diabetes, cancer and vaginal yeast infections are all causes of oral thrush, according to MayoClinic.com.
Teeth grinding or bruxism. Sleeping bruxism is another cause of tongue biting when in sleep. In most cases, it is accompanied by other sleeping disorders such as sleep apnea which causes breathing pauses. Snoring is also a common problem that comes with teeth grinding.