Independent Action is the ability to remain independent, even when rejecting the prana supply from the Master. At the higher ranks, it is also possible to remain for extended periods of time in this world without an established contract. It is both useful and troublesome depending on the disposition of the Servant and the rank of Independent Action. Acting in autonomy from the Master’s prana supply, the Master can concentrate their own prana on large spells, or the Servant will be fine in case they can not supply prana due to injury. The downside is that they can be harder to control and keep by their Master’s side, making the only true way to command them by utilizing Command Spells.
In technical terms, the Independent Action skill extends the time a Servant can remain in the world without a Master or other supply of magic to sustain them, based on the rank of the skill as detailed below.
: The Servant may remain indefinitely in this world even without a Master, but may not use its Noble Phantasm without a steady supply of magic.
: The Servant may remain in this world for a week without a Master.
: The Servant may remain in this world for 2 days without a Master.
: The Servant may remain in this world for a number of hours equal to double his or her Power statistic, or for 1 day, whichever is longer.
: The Servant may remain in this world for an amount of hours equal to his or her Power statistic, rather than half.