General info on how to fuse pets can be found at Toram Online Official Page. In this section I explain some informations that are not written in the official guide, as well as showing you how I create my dream pet Hetero and explain the reasoning behind each fuse :).
Pet Fusion is a process to combine two pets into one new pet. The fusioned pet will start at level 1 with 0% discipline, and clean skill, just like any other pet that you released from a cage. The only difference is that it gets free stat bonus to distribute at level 1, and it can have up to 2 inherited skills.
There are 2 inherited skills: one is taken from pet A, the other one is taken from pet B. You cannot take 2 skills from the same pet, so if you want to do multiple fuses, make sure to fuse the skills on last step.
You can only lock one of Weapon, Type, and Nature. Unlocked ones are randomly chosen from Pet A or Pet B. Just like synthesizing equipments, if both pets has same weapon, type, or nature, no need to lock it.
Level cap = 1+ (Pet A's base level + Pet B's base level)/2
It is important to level up Pet A and Pet B before fuse, otherwise you'll ends up with a low
level cap. This number is rounded down, so make sure the addition of A and B's level is even.
Bonus stat is always equals to new level cap - 1, so the higher it is, the more powerful
is the new pet. This system is very useful to raise the cap of your pet. For example, in my
case, I got Lv 5 Ragging Blow on a Lv 47 Slime, then I raise its cap by fusing with higher
level pets.
Power = Pet A's power + Pet B's power
Power is your pet's weapon attack. Pet's weapon cannot be refined, but its attack power can be
raised by multiply fuses. Please note that a pet cannot get power up if it's current power is
more than its current level. For example, a non fused pet usually have about 30 power at Lv 90.
When two of them fused, you get a new one with 60 power. This new pet will not gain any power
up during its level 1-60, but may gain power up after that. So if you want to raise power, it
is best to fuse with a non-fusioned pet over and over again.
Bonus Potential = (Pet A's potential + Pet B's potential)/10
Again, this number is rounded down, so for best result, try to get the addition close to
multiply of 10. For example if Pet A already has 227 DEX and Pet B currently has 230 DEX but
unfinished training. Raising Pet B's DEX to 233 or 236 gives you the same result after fusion.
So don't waste your discipline % for a stat that won't give you extra bonus after fusion.
Fusion Cost is not much, unless you want to lock dyes. Each dye cost 1m spina, which is too expensive compared to using 1 orb ^^; (as of current market price of orb items). Unless you really really really cannot buy orbs, imo, better pay with orb.
My goals is to have a Black Coryn with Lv 10 Ragging Blow & Lv 10 HP Gain, Bow weapon, and Justice/Sly nature. Type is kinda flexible, preferably Genius or Accurate, but Dodde, Magic Defense, or Magic Attack are still OK (those with base DEX 70 or more). My stat priority is to have 300+ DEX growth potential, then second priority is VIT, AGI, and STR. INT is kinda useless for my build, so it can be any amount. Other skills are optional. Ideally I want Absorb HP and MP Gain, but it'll need tons of luck to get both in one gamble ^^;. By the time of this guide written, I'm just halfway from my goal, mainly because I don't have pet with Lv 5 HP Gain yet.
This is Hetero, my first pet which I want to power up. He's been with me since the first time I research about pet. Back then I didn't know how hard to increase skill level is. He has low skill level, now I know that it's not feasible to cap, so I'm gonna replace the skills. He has good weapon/type/nature, so I will use those :).
My pet who gets Lv 5 Ragging Blow at birth is a Lv 47 Slime, I call him HeteJr. (cuz at that time I thought he looked like a less OP version of Hetero XD). It is capped fast, but I took about 20 hours to grind his skill level to max. His weapon and nature are not good, so I'll need to replace that.
Next, I need a black dye from Kinote. Since Kinote is Lv 70+, it's best to fuse with HeteJr., getting some level cap raise on it. If I fuse with Hetero, its level cap will goes down. I also need a decent Kinote, that is either have good weapon+type or type+nature, so I'll have a chance to replace HeteJr.'s bad weapon/nature.
I wanted a coryn app, so I will need one Coryn pet. Since both HeteJr. and Hetero are low on level cap, it's best to have high level Coryn to fuse with them. I can take the app while raising level cap. I was lucky enough to catch a stray Coryn and gets Lv 4 HP Gain on it. Since it's not Lv 5 at birth, I will just level it to Lv 8.
Fusing HeteJr.(Lv 47) with the Kinote (Lv 77) will only gets him to Lv 63, so I need some more pets for raising level cap. These can be any decent weapon/type/natured pet with failed skill gamble, or even pets without skill, because I will not take the skill anyway.
Now I have all my base pets, I have to design how I'm gonna fuse them based on what lock I can do on each step. Fusing inherited skills should be last. My goal is to have a Lv 90 on the final fuse, so the two final pets' level should be added to 178. The following is my fusing diagram. Note that I don't cap some pets. There are several reasons for it. First because the fused pet's level is rounded down, so level 96 or 97 on "Leve" gives the same result. Second is because leveling up past 75 is quite tiring, and past 90 is getting hard, so I prefer to use several pets with level 70-90 rather than one level 120 for raising level cap. Last is because the power bonus. Fusing with two level 90s means about 2x +30 power, while having one level 120 means about +40 only.
in this fusing process, I locked the dyes 2 times. First is when HeteJr.+Kinote, then becomes white slime with black core. Second is when HeteJr.+Coryn, then he becomes black coryn with white leaf. I used 6 orbs total (3 dyes each), but actually 3 orbs is enough if I don't want to keep the slime app in the middle of the process (I prefer seeing slime when leveling it XD).