Mage Armor

1st-Level Abjuration
Casting Time: Action
Range: Touch
Components: VSM (a piece of cured leather)
Duration: 8 hours

You touch a willing creature and a protective magical force surrounds it until the spell ends.
Target. A willing creature who isn't wearing armor.
Effect. The target's base AC becomes 13 + its Dexterity modifier.
Special. The spell ends if the target dons armor or if you dismiss the spell as an Action.
At Higher Levels. You can target an additional creature for each spell slot above 1st.

Source: PHB 256, SRD

Changelog