Known as 'darksong', a canta malus is a poisonous gift to the mer from Morsa, in mockery of Neria's gifts.
The invocation of some malus spells could get the caster imprisoned: the clepio spells, used for stealing; a habeo, which took control of another’s mind or body; the nocérus, used to cause harm; and the nex songspell, which was used to kill.
Darksong is permitted during war time as self-defense.