Theres actually three quest all for the powerscrolls.. one asks for Magic Residue that gives a 110 scroll, one asks for Enchanted Essence that gives the 115..the last one asks for Relic Fragments that gives 120 scrolls...these quest givers are located by the soulforge near the smith shop. Though this is what Ive been told but you could be right about them only giving up to 115 only but still can scroll bind a bunch of those so still think 7.5mil is way high for a 120 imbuing.