Protego

Protego

(Shield Charm)

3rd-level abjuration

Casting time

 1 reaction (against creature that you see casting a spell)

Range

 60 feet

Components

 V,S

Duration

 instantaneous

Process 

This spell is an attempt to counter a creature starting to cast a spell. If a creature is casting a spell that is 3rd level or lower, its spell fails. A spell of 4th level or higher is harder to counter, and an ability check using your spellcasting ability is needed. The DC is 10 plus the spell level.[1]

At higher levels 

A higher level spell slot can be used instead and when using a 4th level or higher, the interrupted spell has no effect if its level is less than or equal to the level of the spell slot used.[2]

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Harry Potter Spell Description

Protego allows minor to moderate curses and hexes to go back onto the attacker.[3]

Etymology: Latin protego, “I cover” or “I protect”.[4]