soul stone limits

obsidian: one soul stone (same lvl) (student) 1st year

ruby: 2 soul stones (student) 2nd year

sapphire: 3 soul stones (student) 3rd year

emerald: 4 soul stones (academy staff) (1st and second teachers)

aquamarine: 5 soul stones (senior academy staff) ( 3rd year teachers)

ether: 6 soul stones ( vice- academy leader)

diamond: 7 soul stones (academy leader)

bronze: fused with 2 of the 7 soul stones

silver: fused with 4 of the 7 soul stones

gold: fused with 6 of the 7 soul stones

coal: whoever reaches 7 out of 7 will be killed by the yanagi

Soul stones can only activate abilities up to the level of the user.