Boosters. If you go for a rainbow, check out the boosters.
Maximum skill level national mages of Machaka (FFEED? and FDNN?) can achieve with boosters they and FWWAASS pretender can forge if boosters are used to make more items...
2F? +3 Fire = 6F
? +3 Air= 4A (5A with pretender)
? +3 Water = 4W (5W with pretender)
2E? +2 Earth = 5E
? +2 Astral= 3S (4S with pretender)
2N?+3 Nature= 6N
D?+2 Death=4D
? + 0 Blood = 1
They can summon Mound Fiend (they have 3D, right?) which can further summon Wraith Lords and Demiliches, so they can also get powerful mages of Death.
This is without counting in unique items or Rings of Sorcery/Wizardry, which help a lot. There is an excel file that lists all the boosters, you might want to hunt that down if you are interested...
EDIT: Forgot 2Air from the pretender...
