|This spell reduces the chance of projectile attacks striking the caster, by making them significantly easier to dodge.|
Repel Missiles is a level 2 Charms/Air Magic spell which moderately protects the caster from ranged attacks, reducing a missile's to-hit by 0% to 50% of its original value if it is a bolt, or by 0% to 100% if it is a single-target beam. This reduction is done after your shield blocking value has been rolled, so this spell only improves your ability to dodge missiles, not your ability to block them. Increased spell power lengthens the duration of the spell, but does not improve the spell's chance of repelling attacks.
Although this spell is inferior to Deflect Missiles, it's still much better than nothing, especially in the early Dungeon when Deflect Missiles isn't available and you might encounter centaurs (who have made pincushions of many a low-level player). It's also easier to cast, making it useful for hybrid-style casters who might not be ready for Deflect Missiles yet. Knowing either of the two spells is very useful while exploring the Shoals, the Elven Halls, and other areas infested with enemies who love to shoot at you.