Magic Barrier is a Miracle in Dark Souls 2. To cast a Miracle, you must use a chime or Special Weapons that can cast Miracle.
"A miracle encasing the body in a magic barrier.
Increases resistance to magic, lightning, fire and dark.
This miracle is said to shield its caster with the Rock's armor, and was common amongst the wizard knights of Mirrah,"
- Small area of effect, will give barrier to summons if close enough. Lasts 90 seconds.
Increases elemental defenses by 150. This does not stack with Flash Sweat.
"The Rock" is a reference to Havel the Rock, a character from Dark Souls and original wearer of Havel's Set, who used the miracle to combat sorcerers.
- As of Patch 1.04, the duration of Magic Barrier depends on the user's faith. At 10 FTH, even if you meet the spell requirements (lowered with skeptic spice) the spell will last about 20 seconds. At 20 FTH it last about 80 seconds. From 30 to 50 FTH 90 seconds. It is yet unkown if you can extend the duration of the spell by increasing FTH further.