Not long after arriving in Ladylake the game introduces item fusion as the mechanic where two pieces of equipment with the same name can be fused. This increases their stats and combines any skills present in each of the four skill slots, with the following basic rules applies for each:

• If it's empty for both items, the resulting skill slot is empty.
  
• If it's the same skill on both items, it is retained by the resulting item.
  
• If it's used by one item but empty for the other, the skill in use is retained.
  
• If it has different skills on the two items, a new skill is added to the resulting item and locked.

This guide explains the last of these points - the new skill that is created, and how it is decided by the game.

The aim of this is not to be a magic skill calculator (which are available elsewhere). Instead, it is to help players understand the processes the game uses to decide, allowing them to more easily work out skill fusion for themselves when magic skill calculators are unavailable.

To begin, here is a chart of the skill names in the game, with the addition of numbering for each skill and the columns representing skill type as these will be used by the game in determining fusion results.

The simplest and most common form of skill fusion is when both the element and skill type of the two originating skills are different. For this the following rules apply:

• Average the skill number, rounding down.
  
• If the result is one of the originating skills, select the next number that isn't.

The second rule only applies when the numbers are consecutive, when the skill at the bottom of one column is fused with the skill at the top of the next. So it could also be understood as "If the two skill numbers are consecutive, select the number after them."

Examples of this in action:

Example 1:
Atakk (1) + Blokk (8)

• The average is 4.5, round down to 4
  
• So the new skill is Reziss (4)

Example 2:
Spirri (5) + Rangus (6)

• The average is 5.5, round down to 5
  
• 5 and 6 were used by originating skills
  
• So the new skill is Roon (7)

If the element of the two skills being fused is the same, the method is similar but instead of using the skill number it uses the column number. In short:

• Average the column number, rounding down.
  
• If the result is one of the originating skills, select the next column number that isn't.
  
• If there is no next column, select the first column.

Examples of this in action:

Example 1:
Mynd (Fire column 1) + Chein (Fire column 4)

• The average column is 2.5, round down to 2
  
• So the new skill is Roon (Fire column 2)

Example 2:
Blokk (Earth column 2) + Primor (Earth column 3)

• The average column is 2.5, round down to 2
  
• Columns 2 and 3 were used by originating skills
  
• So the new skill is Mirag (Earth column 4)

Example 3:
Acqua (Water column 9) + Invalada (Water column 10)

• The average column is 9.5, round down to 9
  
• Columns 9 and 10 were used by originating skills
  
• So the new skill is Reziss (Water column 1)

This is the most tricky form of skill fusion to understand, as the game balances out the frequency of results by using a method that is not simple to explain in words.

The new skill is decided by using a new element in the same skill type, based on the two original skills' elements. The manner this works allows the following table to display it:


Note that this table is symmetrical (it doesn't matter which order you fuse the items in).

Mechanically I believe this is worked out by placing the elements in a loop:
Normal (1) > Fire (2) > Earth (3) > Water (4) > Wind (5) > Normal (1)

After this, when two elements of the same skill type are combined, an element has the effect "advance the other element x steps and if needed advance until you reach the element not used by the originating skills". For this Normal and Fire add 1, Earth adds 2, Water adds 3 and Wind adds 4.

Examples of this in action:

Example 1:
Plezur (Fire HP) + Gaine (Water HP)

• Shown in the table: Fire + Water = Wind
  
• Calculating with Fire: Water + 1 step = Wind
  
• Calculating with Water: Fire + 3 steps = Wind
  
• So the new skill is Releeph (Wind HP)

Example 2:
Atakk (Normal Status) + Spirri (Wind Status)

• Shown in the table: Normal + Wind = Fire
  
• Using Normal: Wind + 1 step = Normal. The next available step is Fire
  
• Using Wind: Normal + 4 steps = Wind. The next available step is Fire
  
• So the new skill is Mynd (Fire Status)

Skills have a chance to generate with a double (x2) effect on Hard difficulty or above, or even a triple (x3) effect on Chaos difficulty.

When fusion involves these skills, the following rules apply:

• If the input skills are the same, their highest multiplier is given to the output.
  
• If the input skills are different, their lowest multiplier is given to the output.

No averaging takes place here; the fusion of two different skills with one singular and the other x3 does not result in a x2 skill. The output is just singular.

The presence and combination of multipliers has no effect on the choice of the output skill, so fusing Atakk and Mynd is no different to fusing Atakk x2 and Mynd; both result in Difens.

Examples of this in action:

Example 1:
Wresst x2 (9) + Farrest (23)

• The skills are different, so the output has the lowest multiplier which is singular.
  
• The skill types and elements are different so the fusion follows rule 1 above.
  
• So the new skill is Fantum (16), singular.

Example 2:
Gillium x2 (Wind column 2) + Justiss x3 (Wind column 4)

• The skills are different, so the output has the lowest multiplier of x2.
  
• The elements match so the fusion follows rule 2 above.
  
• So the new skill is Releeph x2 (Wind column 3).

Example 3:
Priventi + Priventi x3

• The skills match, so the output has the highest multiplier of x3.
  
• So the new skill is Priventi x3.