Fianto Duri

Fianto Duri is a spell that turn other spells more powerful, used on Protego Maxima and Repello Inimigotum.

However Tom Riddle's unidentified spell could break the shield with the help of the elder wand (even though he was not its true master), his knowledge of the dark arts and his death eater's weakening the shield with their original bombardment.

Known uses

 * This spell was used by professors Filius Flitwick and Horace Slughorn along with Order of the Phoenix member Molly Weasley to protect Hogwarts Castle in 1998.

Etymology
Latin "Fiant", meaning "Become" and Portuguese "Duri", meaning "Hard", all meaning, "became hard"

Appearances

 * Harry Potter and the Deathly Hallows: Part 2
 * Harry Potter and the Deathly Hallows: Part 2 (video game)