The amount recovered from this ability varies with the summoner's summoning magic skill (in addition to any gear that adds to the skill), weather of the area, and the day of the week. Optimal results seem to be obtained with capped summoning skill and matching the summoned spirit with the elemental day and/or weather present in zone.
Using a spirit that is opposite to the day/weather will incur a small penalty to the amount of MP obtained.
Using a spirit that is the same as the weather when it is double weather gives more MP then when it is single weather.
see discussion page for testing data.
(Summoning Skill-50)x(Bonus%)= MP restored. 10% for matching day or weather, 20% for matching day and weather, and 25% for matching double weather.
ex) Thunder spirit on thunder day with thunder weather and 310 summoning skill: (310-50)x(1.2)= 312MP.