Super Guide to Weapon Fusion
I got most of this info from the Japanese wiki, where they figured out the formula for how weapon fusions work to get specific weapons.
Essentially, there are 12 weapons of every type, and each of these weapons is assigned a number from 1 to 12. When you fuse two weapons together, you just add those numbers together to get the number of the resulting weapon. If the result is higher than 12, it just wraps back around to 1; in other words, if it's more than 12, subtract 12. Simple as that!
So for example, you want to make an Angel Bow, because you have heard it has really good homing capabilities and you want to try it out.
First you check this chart to see what combinations can result in bows:
It turns out you can make bows from anything except staves and other bows.
So looking down the first column, you randomly decide you are going to make an Angel Bow from a blade and an arm. What number is the Angel Bow, so we can find out what blade and arm numbers we need to add together?
Well here is a nice list of the item numbers.
I believe this is correct; it's the order the cards are numbered and the order of idols in-game, and every test I've put it through has worked. These are SPOILERS
, some of these weapons take a lot of work to unlock, and they're named after bosses and such.
So we can see that the Angel Bow is number 7. 2 + 5 = 7, we could use blade 2 and arm 5 to make it, which is a Burst Blade and Drill Arm.
Or as another example, Royal Blade plus Artillery Claws equals Ore Club. 5 + 8 = 13, 13 - 12 = 1.
One interesting thing about this is that almost any weapon can be used to fuse almost any other weapon. I mean, think about it...say you want to make a Royal Blade, blade 5. Staves are one blade ingredient and cannons are the other, so let's see which staves and cannons can be used to make blade 5:
1 & 4
2 & 3
3 & 2
4 & 1
5 & 12
6 & 11
7 & 10
8 & 9
9 & 8
10 & 7
11 & 6
12 & 5
...All staves and cannons can be used as part of a fusion to make blade 5! It's just a game of finding the right partner.
If a fusion doesn't work,
i.e. if you try to fuse two weapons to make a new one and all you see is an X and question mark, it means you haven't unlocked that weapon yet. Play the game more, explore more thoroughly in every even-numbered chapter
, complete more treasure hunt challenges. Eventually you will be able to fuse anything with anything.
According to the wiki that revealed this
, there are some exceptions to this rule. You'll expect to get a staff and end up with a sword instead. I have no idea why, perhaps there are some small programming errors. If a certain combination doesn't turn out as expected, I'm sorry, but this addition rule for fusion works the majority of the time.
Oh yeah, one other thing: to my knowledge, nobody knows how to tell which stars and abilities get carried over yet. It's bound to be a complicated calculation.