“That enchantment Doremil sang deep into the world, enmeshing it within water, stone, earth, and air. By it, they tied all magic to life and blood. But while the curse succeeded, the plan did not. War waged on, and Doremil despaired.”
Nākadmazul, “Of the Binding and the End of the Days of Wrath”
The Isencurse was Doremil’s first attempt to curtail the violence of the Last War. Seeing that the art of magic had been turned to ill purposes, Doremil decided to enchant the world and alter its nature, making it so that spells now required the consumption of blood to be cast. Their plan failed, for the Kembar continued to do battle despite the added costs.
Doremil’s next attempt to end the War would be the Binding.
Etymology
Isen is an archaic form of English “iron”. The Isencurse is so named because it made the iron (or copper) found in blood compounds a required component of spellcasting.