I wil give credit to Merchantmace, Avanthar, Elizabeth, and Caribou for providing me with the intro to spellcrafting and contributing to the compilation of the information herein.
I noticed a recent thread looking for more info on spellcrafting. There are a few guides in these forums, but I will compress the info here.
There are three items used; Book of spellcrafts, magic jewels and spellcraft jewels. All three can be looted from the corpse of the "Guardian of Magics" in Hythloth. Magic jewels and spellcraft jewels are additionally acquired from bosses located deep in dungeons. Crusty treasure chests also have magic jewels inside.
Elizabeth's guide here:
How to get the spellcrafting book: Defeat the Hythloth dungon boss, aka "the magic boss", for a chance deed that may or may not give you the book. The boss can change into three forums (human, wyrm, imp) and can self heal. She/he also spawns a monster known as 'acid imps', which leave pools of dangerous acid once they die. Use an invis cloak and cast metor swarm between hiding. Corspe skin (on the boss) also is usefull. Do not use a weapon. Once you get the spellcrafting book, it will bond to you so it cannot be sold. Thanks Liz!
The book of spellcrafts is looted empty, all 50 recipes (spellcraft jewels) can be added to the book in the same way as one would add a scroll to a spellbook. (Drag over and drop)
Every attempt to apply a property to an item will consume 3 to 5 magic jewels.
Upon each try, you can miss, hurt yourself, destroy the object or apply the property between minimum and maximum value. Applying the same property twice will reapply between min and max value, it can be lower or higher than the previously added one.
A maximum of 5 different properties can be on an item.
Each property applied is limited to a certain slot(s). See breakdown below.
Jewels
Shields
Armors
Hats
Weapons
Instruments
NA- Not Applicable
Enhancement______________Min___Max--- Item types
str bonus ------------------------ 1 to 8 --- J
dex bonus ----------------------- 1 to 8 --- J
int bonus ------------------------ 1 to 8 --- J
hp bonus ----------------------- 1 to 8 --- A + H
stam bonus --------------------- 1 to 12 -- A + H
mana bonus -------------------- 1 to 8 --- A + H
physical resist ------------------ 1 to 15 -- A + H + W + J
fire resist ----------------------- 1 to 15 -- A + H + W + J
cold resist ---------------------- 1 to 15 -- A + H + W + J
poison resist ------------------- 1 to 15 -- A + H + W + J
energy resist ------------------ 1 to 15 -- A + H + W + J
hit point regeneration -------- 1 to 2 --- S + H
mana regeneration ----------- 1 to 2 --- A + H
stamina regeneration -------- 1 to 3 --- A + H
faster cast recovery ---------- 1 to 3 --- J
faster cast speed ------------ 1 to 1 --- S + W + J
lower mana cost -------------- 1 to 8 --- A + H + J
lower reagent cost ------------ 1 to 20 -- A + H + J
mage armor ------------------- 1 to NA -- A
mage weapon ----------------- 1 to NA -- W
spell channeling --------------- 1 to NA -- S + W (edit, this does not give casting penalty)
spell damage increase -------- 1 to 20 -- J
hit cold area ------------------ 2 to 50 -- W
hit energy area --------------- 2 to 50 -- W
hit fire area ------------------- 2 to 50 -- W
hit physical area -------------- 2 to 50 -- W
hit poison area ---------------- 2 to 50 -- W
hit dispel ---------------------- 2 to 50 -- W
hit fireball --------------------- 2 to 50 -- W
hit harm ----------------------- 2 to 50 -- W
hit lightning ------------------- 2 to 50 -- W
hit magic arrow --------------- 2 to 50 -- W
hit lower attack --------------- 2 to 50 -- W
hit lower defense ------------- 2 to 50 -- W
hit leech hits ------------------ 2 to 50 -- W
hit leech mana ---------------- 2 to 50 -- W
hit leech stamina ------------- 2 to 50 -- W
use best weapon skill -------- 1 to NA -- W
weapon damage increase ---- 1 to 50 -- W + J
swing speed increase --------- 5 to 30 -- W + S + J (+5 max on jewels)
hit chance increase ----------- 1 to 15 -- S + W + J
defense chance increase ----- 1 to 15 -- S + W + J
enhance potions ------------- 2 to 25 -- J
lower stat requirements ----- 10 to 100 - A + W + H
luck --------------------------- 1 to 100 - A + W + H + J
reflect physical --------------- 1 to 15 -- A + H
self repair --------------------- 1 to 5 --- A + H
night sight -------------------- 1 to NA -- A + H + J
slayer ------------------------- 1 to NA -- W + I (randomly applies, can be super slayer)
durability ---------------------- 5 to 250 - A + W
Advanced Spellcrafting.
It is possible to spellcraft an item with greater than 5 mods on it by reapplying and existing enchant. This will re-roll the value of the mod. For example, the Ch'vayre's Shades have many low intensity mods on them. They count as jewelry and you can apply any Jewelry compatible mods onto it that it currently has and hope that they increase. Note: This may DESTROY your prized possession. Note, the resists don't re-roll if reapplied.
When enchanting set items the set mods don't count toward the 5 cap. If you enchant it with something it will have when full set is present your enchant will be deleted.
The golden twiggy is capable of adding a new mod to an item from a list of quite a few possible mods. This opens up some possibilities. If you use a Golden Twiggy to place Damage Increase onto a ring, you are then able to spellcraft Damage Increase on the ring even if it has over five properties already. This is because you have forced a property to exist on the item, and we know from above that we can reroll existing properties by re-enchanting the same property again.
I have recently discovered that resists on armor can be spellcrafted and rerolled regardless of how many properties are on the item. This opens up a lot of opportunity for resists.
A FEW REAL EXAMPLES
A typical spellcraft would be done on an item that has less than 5 mods on it. Lets say the Titans Hammer which has 4 total. They are:
Hit Chance 15
Strength Bonus 15
Hit Energy Area 100%
Damage Increase 50
On this item, you can spellcraft an additional Weapon property. Hit Life Leech for example. The Life Leech spellcraft, if successful, will apply between 2 - 50 Life Leech. You would then be at 5 properties total and cannot add any new ones.
Here's how existing properties work...
Say I have a crafted sword with the following
5% hit lower defense
Damage Increase 25%
Hit Fireball 5%
Defense Chance Increase 10%
Self Repair 5
You would initially think you can't spellcraft because there are already 5 existing properties, but in fact you can reroll any of the existing properties that you have compatible spellcrafts for (compatible as in the spellcraft works on the item type).
Applying the spellcraft of an existing property (in this case we'll say Hit Lower Defense), will not get additional points added to the existing property, but you will reroll the property in its entirety between 2 - 50. You can keep doing this until you get the desired value you want as long as the item doesn't break and you don't run out of charges.
I will continue to add flavor as questions come in