I obtained the learning methods to Rank F (and eventually to Rank B) Spark a while back, and since a lot of people are waiting for it, I thought of bringing the information over to here and also to add in a few more observations on it.
Much thanks go to Majikaru for helping me out with the spark questions back then.
JP page on spark: ???/???/???? - Mabinogi Wiki* (First)
CN yydzh page on spark: Skill/???/??? - Mabinogi Wiki
The information over there is taken from JP wiki so it should be the same.
This is the NA wiki page for Spark: Spark - Mabinogi World Wiki
Spark does not make you invincible. It's knock-back property to any monster protects you (giving some sort of invincibility for a few seconds), but you have to know that the speed of attack will slow down towards the end and you might get hit by the monster who will retaliate back. (No video proof, but I tested Spark against a G11 Peaca mission Red Ghost).
The damage isn't great, but I managed to get a few finishing moves off Peaca monsters in a Dunbarton ghost attack event over here through the use of Spark.
Crystals are fairly difficult to make. It's recommended to get enchants/titles that increase crystal making success rates and also to prepare materials beforehand and wait for Samhain and rain to make these crystals. The main ingredients are royal jelly and you can get them by opening beehives, at a uncommon chance. The chances of getting royal jelly from the beehives are estimated to be between 10-15%. Beehives are obtained by hitting beehive trees on the map between Tara and Taill.
Spark Crystal Making Success Rates
Rank B alchemy mastery
Normal day, cloudy: 32% (28%)
Samhain, cloudy: 38% (34%)
Samhain, Level 20 rain: 41% (37%)
Rank D, Samhain, rain: 44%
Rank B, Samhain, rain: 51% (I think...)
Not tested with thunderstorm.
Brackets are speculated rates without alchemy mastery.
+2% if using prefix Difficult enchant. (Suffix -CP enchant is called Trouble on CN server so probably there will be changes in NA on the names.)
Based on weather forecast: Erinn Long Term Forecast
Level of rain does not affect.
Of all the pages,
Spark 1 will be pricey (might rival price of spark 2), and people usually do Taill's advanced level and hard mode Provocation. You need a team of 3 to go in.
Spark page 2 is the most expensive (at the start) because it is dropped on the hard mode mission "The Enemy Behind", at a 0.86% success rate for hard mode. That means you have to be at least level 1000 to go in. It is hard mode only for CN and JP servers. TW servers should be the exception because they get the page drops from advanced mission as well (level 300+), the last time I checked. This is a 1-2 person mission.
Spark 3 is the easiest page, where you get from Queer book in a Tara Castle mission, "Spirit of Partholon". I think it's a 1-5 person mission, with limitation of intermediate level and above.
Spark 4, people usually get it from doing the 1-2 people Taill. Crag Cow mission and a few other missions (such as Provocation) with Crag Cows. Limitation of intermediate level and above.
Spark 5 is from intermediate and above levels, boss of the Tara Castle mission "The Other Alchemists". The boss is a giant Snake Lizard.
Spark 6 is from intermediate and above levels, boss of the Tara Castle mission "Spirit of Partholon". The boss is called Death God, which rides a Death Steed. Death God uses a flying axe attack which hurts very badly, and is impossible to dodge (although it is said in a yydzh discussion thread that you are meant to use evade to dodge it).
Spark 5 and 6 can be difficult to get. There are plenty of people who are looking for Spark 6 in particular as the Death God boss can be challenging.
Spark 7 is from the 1-8 person Taill. mission Defeat Shadow Wizard quest, end chest, intermediate level and above.
Spark 8 is from end chest of intermediate and above levels of the Tara Castle mission "Spirit of Partholon".
Spark 9 is from end chest of Tara mission "Their Way" (zombie grind mission). Limited to only Advanced level and Hard Mode.
Spark 10 is from Taill missions Sacrifical Offering and Defeat Shadow Wizard, Advanced and Hard Mode levels. You can also have a chance at this page with Evidence Clues mission of G10. Only the male shadow wizards will drop this.