Hey there. I'm going to preface this by saying that if you want to rank this skill, it's going to be a very painful road. No one really sells materials so it'll be mostly self grinded.
Everything here out after is going to be a SPOILER so if you want to discover the content on your own, do not read further.
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What's special about runecrafting compared to the other skills is that you need to learn recipes through skill books you find in Library Normal, Library Observatory, and Reoite. Here's a checklist of books that are useful for ranking the actual skill:
Book of Arcane Locks - Library Normal Chest room/Endchests
Book of Protection - Library Normal Chest room/Endchests
Book of Dust - Library Normal Chest room/Endchests
Book of Magic Gems - Library Normal book piles/Endchests
Book of Frostbite - Reoite Quest Chain
Obtaining your table:
Quest chain stuff here (I don't have the pictures for the questchain). After you finish the series of quests you receive at level 650, you should have book exchange unlocked (don't trade in any Strange Books of Arcane yet). Hopefully at this point, you have found a Book of Arcane Locks in Library Normal. After reading this book, runetables within Library, as well as your future personal runetable, will have stored these recipes. You will need the following:
After obtaining these items, you can find a rune table in the third floor of Library Normal (or 2nd floor of Library gem) to craft your personal rune table.
Ranking the skill:
The Soul spreadsheet of megadrops also has all the books as well as the ranks of each recipe.
https://docs.google.com/spreadsheets/d/1JiIumd3ZjKkaNDiszhAdSo2mwj8jmd35aOHpshHiS24/edit#gid=1002532729
You will need a PropPet Interaction, which you should receive when summoning the table. Should you throw away this item, you can always buy another one from Shyla for 5k gold under the Premium Items tab. As the runetable itself is a pet, the skill is linked to the pet and can be used to interact with the pet (for crafting) with this item mentioned prior.
As most crafting skills are, you are able to rank up the skill after successful crafts of items of the
same rank or
one rank higher. You are also limited to crafting items of one rank higher than your runecrafting skill. In addition to providing the materials necessary for each craft, each craft also requires
a lot of MP per craft, thus I highly recommend using MP elixirs from Monday's Advanced Play service to nab yourself a couple MP elixirs. You'll also notice that a lot of the crafts will require more MP than your table has. You can feed up arcane cores to your table, which will allow your runetable to increase its MP pool permanently.
This is what I used at each rank personally (probably the easiest path).
Tier 1: (Requires 5 crafts, 3 AP, 1 Arcane Light Fragment per rank)
rF: Great Arcane Key (Library normal Floor 3, 5 times)
rE: Magic Powder
rD: Defense Ward
4 Runestones, 1 Magic Sapphire to progress to Tier 2.
Tier 2: (Requires 12 crafts, 4 AP, 5 Arcane Light Fragments per rank)
rC: Elite Magic Powder
rB: Fire/Ice/Thunder Ward
rA: Magic Spinel*/Burning Magic Powder
r9: Burning Magic Powder
5 Runestones, 1 Magic Aquamarine to progress to Tier 3.
Tier 3: (Requires 30 crafts, 6 AP, 9 Arcane Light Fragments per rank)
r8: Ice Flute
r7: Magic Diamonds
r6: Magic Diamonds
r5: Congrats you're at the cap (as of now)
*For magic spinels, you may need the assistance of a magic sapphire to increase your runetable's MP pool further, as it is very MP intensive for the rank.
Materials that you will need a lot of:
Arcane Cores (early ranks for boosting max MP and wards)
Spirit Powder (tons)
Arcane Light Fragments (tons)
Holy Flames (marginal, do PTJ)
Materials that are seemingly useless:
Inscribed Metal Shards
Stone Fragments
Rune Stones