= , "even"
This sentence would appear to mean literally "So long as I continued to be in the condition of a disciple of Daikai-oshinsama . . . even I was able to use the power of revival/resurrection". Less literally "Even I, so long as I remained a disciple of Daikai-oshinsama, retained the power of resurrection".
Note that while = "is", = "continues to be", "remains".