Synthesis is the term used for the process involving the upgrading of a weapon's attributes, which eventually can lead to the evolution of said weapon into a more powerful form. Weapon experience comes in the form of ABS (short for "Absorption"), which is gained by defeating enemies, stronger enemies drop more ABS. The Ridepod and playable monsters can also absorb ABS, but the former uses it to purchase new upgrades and the latter only uses it to level up.
Dark Cloud[]
In Dark Cloud weapons have slots in which one can place attachments. An attachment's sole purpose is to improve a weapon's attributes. Once a weapon has absorbed enough ABS (the blue bar) it will be eligible for an upgrade, which adds a "+1" (or a higher incremental number) to the weapon's name. Upgrading will slightly improve a weapon's base attributes (attack, speed, endurance and magic) as well as absorbing the attachments placed in its slots, thus permanently gaining those attribute bonuses. Weapons have a certain ABS requirement before they can upgrade, with more powerful or higher leveled weapons having higher requirements.
Once a weapon reaches +5 it can Status Break, which involves sealing the weapon into a Synth Sphere (or SynthSphere), which retains only 60% of its entire base stats and whatever attachments it had in its slots. Attempting to Status Break a weapon at +4 or lower will cause it to only retain a fraction of its original attributes, making such a Synth Sphere effectively worthless. Synth Spheres also retain a weapon's original abilities, thus synthesizing those is the only way to create a powerful weapon with multiple abilities.
Note that only the blue slot on a weapon can house a Synth Sphere, of which each will always have only one, though more powerful weapons will have more and more normal slots. A powerful Synth Sphere can also be repeatedly moved around, only boosting weapons as long as they are used in case you want to level a weak weapon. It is possible to kill a monster and switch weapons to gain the ABS on the second weapon, but only if the switch is performed before it has faded out. This does not work with switching characters, as the ABS will be lost.
The Abs Up ability can be used to improve the rate at which ABS is gained. A Mystery Circle can also fill up your weapon's ABS
Dark Cloud features four trophies involving Synthesis. Status Breaker, a bronze trophy is awarded upon using Status Break to create a SynthSphere. Using Build Up to turn a weapon into a new weapon results in the silver Even Stronger trophy. Upgrading a weapon ten times will leave you with the silver Weapon Collector trophy. Lastly the Specialized Weapon gold trophy will be gained upon maxing out any attribute on a weapon, without the numbers gained from any slotted attachments.
Dark Chronicle[]
In Dark Chronicle weapons no longer have slots, and fewer attributes. Instead they automatically level up, gaining Synthesis Points as they do, ranging from three to six depending on the weapon, the stronger they are, the more points they gain. ABS now appears in the form of small blue grains (eight per enemy), which is automatically absorbed by the weapon that was used to kill the enemy that dropped it. It is possible to switch weapons and instead let the ABS be absorbed by a different weapon, or to switch characters and have the other character share the ABS between both her or his weapons. Weapons need more ABS as they grow stronger, either through Build Up or leveling up.
Instead of attachments and slots it is possible to spectrumize almost any item into a Synth Sphere, which usually retains only +2 of a specific attribute. Crystals will grant +3 (excluding the Power and Protector Crystals, which is made up by weapons automatically gaining Attack and Durable points on a level up), and gemstones still grant a lot more points. Any spectrumized item becomes a Synth Sphere, though as before only +5 weapons can become stable Synth Spheres. A weapon Synth Sphere will retain 60% of its total stats (rounded down), except for Attack, which is dependent on the Attack level of the spectrumized weapon and the target weapon.
Using spectrumize to turn a weapon into a Synth Sphere will award you with the bronze Weapon Synthesis trophy.
Synth Sphere stat growth[]
If the Attack stat of the latter (X) is greater than or equal to the Attack of the former (Y) then X will only receive 25% of the Y's Attack.
On the other hand, if Y, the Synth Sphere, has more Attack than X, the receiving weapon, Y will gain a bonus of Attack, on-top of the default 25% minimum. Said bonus is 75% of Y's Attack minus X's level of attack. Thus the greater the difference the less Attack is lost overall when synthing a powerful weapon to a weak one.
ABS[]
Each weapon has a required level of ABS before it will level up. The first two levels will require the same amount, the third will require half as much and the fourth will require double. The pattern here is that each level increases the needed amount by half of the initial required number. Higher weapons will have higher base amounts, and thus require more ABS in the long term. The formula for the required amount of ABS for any leveled weapon is thus:
And in order to reach a specific level, this formula will result in the total required amount:
The maximum level a weapon can reach is 99, though they will still absorb ABS, earn Synth Points and gain attribute bonuses on a level up. The required number of ABS will not increase however. As enemies always drop eight grains of ASB each, some enemies with less than eight ABS or a number indivisible by eight, will drop ABS with a fractional amount. This is normally collected by any weapon, and is only rounded up when the weapon is eligible for a level-up. If say a weapon needs 32 ABS for level +1, then it will do so at 31.25 or 31.75 ABS, but not at 30.75 or 30. Lastly, ABS gained that exceeds the amount needed for a level up is lost entirely. If your weapon only needs two points to level up, but picks up a grain worth 20, then the other 18 are gone.
The ABS Up ability can be used to improve the rate at which ABS is gained, and the Angel and Devil Coins can also impart a small ABS bonus. If a weapon is to lose all of its WHP, then it will lose half of its current ABS.