The Battle of Estremoz is a battle fought around EstremozW, Alto AlentejoW, PortugalW between Heraclius Hero a.k.a. Herpo the Foul and the four founders of Hogwarts Godric Gryffindor (canon), Helga Hufflepuff (canon), Rowena Ravenclaw (canon), and Salazar Slytherin.
Hero's attack is motivated by his opposition to the use and teaching of powerful magic and one or more specific prophecies (canon) about the founding of Hogwarts.
Hero's army includes terrasque and dementors.
The time of the battle is unknown, though it could have happened around the time of the founding of Hogwarts, i.e., in the 12th century.
The Battle ends with the defeat and death of Hero. He will later revive by means of his Horcrux(es).