By default, failing a spell still uses all the spell points required to cast it. Mana control is a useful utility skill which can reduce this penalty. At best it will save all but one of your lost spell points, but it is highly random and even at high skill levels sometimes won’t do anything at all.
The best way to save spell points is to not fail your spells, but this skill is a big help against bad luck, guild limitations, or a lack of experience to study magic to high levels of ability.
It used to be named “skill that saves sp”
The in game help reads:
Skill duration: random. Type of skill : neutral skill. Affecting stats: Wi. It uses no endurance points. Magic, due to its very nature, is not a totally reliable tool. Even the most powerful wielders of magic can fail in their spells. Unfortunately, once a caster attempts to use a spell, he must supply every bit of energy and concentration to the spell, whether or not it succeeds. While some may argue that the first step is to not fail in the first place, many find it necessary to be able to reclaim the lost energy that they expend, should a spell fail. By using what some refer to as, a reflex action of the mind, upon failing a spell, they can attempt to regain the energy they put into the spell, before it disappears into the void, lost forever. This is one of the few arts that challenges even the most gifted, and its results are very sporadic. It is said that those who are exceptionally wise are better at reclaiming the lost energies.