Spells were graded based on the level of mana poured into conjuring them and as well their use.
Chanting were simply words used to control the flow of mana in a certain pattern when creating powerful spells.
Generally, each spell created was ranked into tiers, the highest tier being the 10th tier spells.
Their destructive power was would put several nuclear weapons of mass destruction to a shame.
Simply put, with a tier ten spell, one was sure to wipe out a kingdom from the face of the earth.
Considering the power, they were quite rear to find, and even harder to learn. Asides that, the purpose of the spell also determined how much mana it would require.
Attack spells usually took more mana, defence took way more when using powerful defense objects.
There were also other spells like, supportive, and many much more. Healers were on a totally different scale altogether. It could be considered another path to the use of magic.