This magic (an experiment crafted by the wizard Sammaster during his early training) protects its caster against enchantment/charm magic. The caster receives a normal saving throw vs. spell against all enchantment/charm spells that normally allow no saving throw and a +3 bonus on saving throws against enchantment/charm spells that do allow a saving throw.
A faint, high-pitched, continuous singing sound surrounds the head of a being protected by charmthwart. The sound is audible 20 feet away in quiet conditions and about 10 feet away in conditions of average or normal noise.
Charmthwart can be ended instantly before its expiration by the silent will of the caster.
