Eudemon Quality: 
The overall strength of a eudemon is reflected by its quality.  The quality of eudemons are as such:
Weak > Common > Average > Good >Strong > Superior >Silver >Gold >Super 
Super eudemons receive a star value that increases your potency. 

The quality of eudemons is based on a point system.  At 100 points, the eudemon becomes of super 1 star quality.  For every 100 points, the eudemon gains another star.  You can increase the number of points your eudemon is worth through composing. 

Eudemon Stats:

Eudemons have a different stats system than your character.
Initial Stats = These are the stats the eudemon has at level 1.
Growth Rates (GR’s) = These are the rates at which the eudemon’s stats grow per level.  Each stat has a GR, which can be determined at Nels in Market (70,184).  She will also tell you how many points your eudemon is worth.
You can also self determine the GR of each of your eudemon’s stats manually: 

Let’s say we have a eudemon with an HP of 2050, an initial HP of 50, and a level of 20.
Take the current HP minus the initial HP:

2050-50=2000

Divide by the level of the eudemon:

2000/20=100

The HP GR of this eudemon is 100.  This can be done for any stat.

The stats eudemons have are:
HP = The amount of life your eudemon has.

Min Atk / Max Atk = The minimum and maximum physical damage your eudemon can do.

Def = Defensive power of your eudemon versus physical attacks.

Min Matk / Max Matk = The minimum and maximum magical damage your eudemon can do.

Mdef = Defensive power of your eudemon versus magical attacks.

Luck = The luck of your eudemon

Eudemon Composing:

Eudemons can be composed at Professor Aderes in Market (95,205).  There are many types of composition, each of which has a different effect.  For each composition, you must have a main eudemon (the one that will be upgraded) and a minor eudemon (which will disappear after the composition).  Different types of compositions have different requirement for the main and minor eudemons.  When you compose, the main eudemon will become stronger and will be reborn as a level  eudemon.  It will return to its original level after it reaches a certain milestone:

If the eudemon is less than super 5 star quality it will return to its original level upon reaching level 50.

If the eudemon is 5-9 star quality it will return to its originial level upon reaching level 60.

If the eudemon is 10+ star quality it will return to its original level upon reaching level 70.

Major Attribute Composing = Increase the major attribute(s) of your main eudemon.  A warrior Patk has the major attributes of Min Atk and Max Atk.  A warrior Pdef has the major attribute of Def.

Requirements:

If main eudemon less than super 5 star quality:

1) Main eudemon must be at least level 50

2) Minor eudemon must be at least level 20

If main eudemon has 5-9 star quality:

1) Main eudemon must be at least level 70

2) Minor eudemon must be at least level 20

If main eudemon 10+ star quality:

1) Main eudemon must be at least level 70

2) Minor eudemon must be at least level 50

3) Minor eudemon must have at least 1 star quality (this requirement goes up as your main eudemon’s star value increases)

If main eudemon 15+ star quality:

1) Same rules as 10+ star quality

2) Additionally, minor eudemon must be of the same element (air, earth, fire . . . etc) as the main eudemon

*note – Thunder eudemons may compose with any element of eudemon.

Sub-attribute Quality Composing

Sub-attributes refer to all the attributes beside main attribute. For example: MageM-Atk`s sub-attributes are P-attack, P-defence, M-defence and life.

Sub-attribute quality composing is 100% successful.

After the sub-attribute quality composing, the minor eudemon will disppear and the main one return to level 1, at the same time, its quality will be improved.

Requirements for sub-attribute quality composing:

The main eudemon must reach level 70, its quality will be improved by absorbing part of the exceeded part of the sub-attribute growth rate the minor eudemon over the main one.

The minor eudemon must reach level 40 and at least one of its sub-attributes exceeds the main one`s. You can judge this by the eudemon grading of Nels. But if your eudemon didn`t meet the requirement, it can`t be placed in the composing panel.

After composing, the eudemon will jump to its original level at the same level with eudemons after main-attribute composing.

Initial Attribute Composing = Increase the ini. stats of your eudemon.

Requirements:

1) Main eudemon must be at least level 70

2) Minor eudemon must be at least level 40

3) Minor eudemon must have at least one initial stat that is higher than the main’s initial stat.

Luck Composing = Increase the luck of your eudemon.

Requirements:

1) Main eudemon must be at least level 70

2) Minor eudemon must be at least level 40

3) Minor eudemon must have more luck than the main eudemon

*note – if you have a eudemon clover in your inventory, you can use it to maximize the amount of points your eudemon receives upon composition.  The system is based off of dice rolls and the eudemon clover will insure that you receive all 6’s from the dice.

Eudemon Loyalty:

Eudemon loyalty determines what your eudemon is willing to do with you.  A eudemon with loyalty less than 50 will not allow you to summon it.  A eudemon with loyalty less than 100 cannot be converged with.

You can increase loyalty by keeping the eudemon summoned and by allowing it to fight with you.  When eudemons are summoned, they will both always have the defense of the one with the best natural defense.  If a eudemon with a defense of 200 is summoned along with another eudemon of defense 1100, both will have 1100 defense.

You can check your eudemon’s loyalty by passing your mouse over the heart-shaped picture in its details screen.