Fusion
Like standard Power Amp Techniques, Fusion is a technique used by fighters to greatly increase their power.  Fusion, as it's name suggests, is the literal joining of two (or sometimes more) fighters into a single being; mind, power, and body.  Though rare, there are numerous types of Fusion to be found in the Dragon Ball Z Universe.  Some are racial, allowing most members of a single race to instinctually know how to perform, some are techniques that must be learned like Power Techniques, some are forced upon others, and some are bestowed.  In any event the outcome is always the same; a new singular being that is the combined power of those involved, creating a new powerful fighter.

The particulars of the Fusion depend on the type that it is, and the being that is created form the Fusion is as varied as the types and the persons involved.  Each type of Fusion creates a unique being that is explained in their descriptions.  Fusion is a very rare ability, and while most have no true Power Level requirements, these techniques are typically reserved for only the most powerful fighters in the Universe.

Absorption
While not like standard types of Fusion, Absorption is the first type that will be discussed.  Unlike most other forms of Fusion, Absorption is not something that is typically willingly performed by both parties and is usually forced upon one, or more, victims.  The most famous fighters that used the technique of Absorption are Cell and Majin Buu.  Typically Absorption is a technique known by an individual and forced upon a victim.

Absorption is not a technique that can be learned, and it is not something that can be picked up through training.  Absorption is unique in that it is either bestowed to unique beings upon creation, no matter the circumstances (Cell was a product of science, and Majin Buu was created by magic), or it is a genetic mutation in extraordinary individuals.  Absorption is a very powerful technique for fighters and can only be used by players under the following conditions: 1) Absorption must and can only be selected upon character creation.  It's not something that can be learned later in the fighter's life.  2) Absorption is a complex technique to use and requires the expenditure of three Power Technique slots (so most new characters can only know Absorption upon character creation), and 3) The GM must okay the use of Absorption by the player.  This is a form of Fusion normally reserved for powerful villains of a Saga and is a very powerful technique to put in the hands of a PC, a GM should weigh the consequences of allowing PCs the use of this ability.
To absorb a victim the absorber must have a physical way of drawing the victim into their body; Cell had his scorpion-like tail and Buu was able to expel globs from his body and manipulate them to engulf his victims and draw them into his body.  Physical size does not seem to be an issue when absorbing an individual.  When Buu absorbed his first victim, the Southern Supreme Kai, he was in his smallest state and South Supreme Kai was nearly twice his size.  But still Buu was able to absorb him.  Also, what happens to the victim once they are inside the absorber is sometimes a mystery as well.  No one really knows what happened to Androids 17 and 18 when they were absorbed by Cell, but we know that those absorbed by Buu were held in stasis within cocoons that Buu called "people pods."  Obviously the power that allows the user to absorb victims also allows them to shrink their victims down for "storage."

Once a victim is absorbed however, not all hope is lost, in rare circumstances they can be rescued.  Gohan's attack during the Cell Games was powerful enough to cause Cell to expel Android 18's body from him, thus freeing her and reducing his power.  Goku and Vegeta were able to enter Majin Buu as Vegeto and free their friends as well, carrying them outside to safety.  In these instances the villains lost all of the power granted to them by the Absorption (although Cell's regeneration "remembered" the powers of when he had Android 18 absorbed).
Requirements:
The being must be created with the ability of Absorption (with the GM's permission)

Stat Improvements:
The following stats of the absorber are modified by their victim:
Absorption is not Fusion in the traditional sense.  The power is stolen from the absorber's victims, not something that is freely given, so the bonuses aren't as great as when two (or more) parties willingly fuse.  As such, the absorber gains the following benefits from their victim:
  • Half of their victim's Power Level (rounded down)
  • Half of their victim's Power Up (rounded down)
  • Half of their victim's Skill Points (rounded down)
  • 1d4 of their victim's unique Power Techniques (determined by the GM)
Note that an absorber can absorb more than one victim at a time, and would then gain the above mentioned benefits from each victim that has been absorbed!

Duration
Theoretically forever.  The technique of Absorption draws the victims into the absorber's body and makes them a permanent part.  However we have seen that under some extraordinary circumstances those who have been absorbed can be rescued/released from the absorber (the particulars should be unique for each absorber and left to the GM for the details).
Channeling
Channeling (or Power Channeling) is the most basic and common form of Fusion in the Dragon Ball Z Universe.  This is also the only form of Fusion that is known/able to be performed by all fighters that know how to manipulate Ki energy.  Channeling is simply the act of concentrating on an individual, the recipient, and channeling all of your Ki energy into them, thus making them stronger - albeit temporarily - for the fight.  The most famous incident of this happening was when Gohan, Future Trunks, Piccolo, and Vegeta channeled their power into Goku on New Vegeta when he was fighting Broly.

To use Channeling, the user must either have line of sight on the recipient or be able to sense were the recipient is (either through Sense Power Level or a Scouter).  After that all the user has to do is focus on the recipient and feed as much of his own energy to the target fighter as he wishes.  The energy of the sender travels at a quick rate of 1 Move per point of Power Up.  So someone with a Power Up of 130 could channel his energy at a rate of 130 Move per Phase.  Also, the user can only channel as much energy per Phase as his Power Up.  So the same fighter from the previous example could channel 130 energy points, at a rate of 130 Move, per Phase.

This is a very basic form of Fusion (if any of the Fusion forms can really be referred to as "basic"), and all that the users of Channeling can do is empower the recipient with more energy than he would normally be allowed by his Power Level.  Channeling requires constant concentration from the user to maintain the power boost to the recipient.

Requirements:
Must be able to manipulate Ki energy

Stat Improvements:
The following stats of the recipient are modified when having energy channeled to them:
A fighter using Channeling can temporarily increase a recipient's Power Level above what it could normally be.  The fighter that is channeling power into the recipient can channel as much power as his Power Up at the same number of Moves (as explained above).  The fighter can only channel as much power into the recipient as he currently has powered up at the time Channeling is used (so if the user has a Power Level of 2300, then only 2300 energy points can be channeled).  Note that a user does not have to channel all of their energy into the recipient, they can limit the amount of energy channeled if they wish.

Multiple users of Channeling can channel their energy into a single recipient (as we saw when Goku fought Broly).  This give the recipient an increased Power Level and a nearly constant Power Up.  The recipient can receive an amount of power per phase as is channeled into them, and they are not limited by the amount of power they can be fed.  Unlike when a fighter Powers Up on their own, those that are the recipient of Channeling can have their Power Level pushed beyond their maximum.  This boost is temporary though as the recipient will burn off energy (much like a Super Saiyan) until their Power Level is brought down to their personal maximum.

Example: Piccolo has 1600 Power of his 3400 Power Level left, and Tien has 800 of his 1830 Power Level left.  Both of them are going to channel their energy into Goku who is at 7000 of his 8000 Power Level.  Piccolo has a Power Up 220, meaning that he can channel 220 energy into Goku at 220 Moves, and Tien has  Power Up of 210.  This means that when both fighters channel their energy into Goku, he can receive 430 energy per Phase.  Between the two of them, Goku can also receive a maximum of 2600 energy (Piccolo's 1600 + Tien's 800).  When all the energy is channeled into Goku, the 2600 + his 7000 = a total of 9600; 1600 more than his maximum Power Level.  Whether he uses all of the channeled energy or not, Goku will burn off the residual energy until he is brought down to his normal 8000 Power Level.


Those using Channeling would use the Power Up numbers they would be at for powering up their own Power Level.  Also, a fighter must Rest after Channeling power, just as they would between power ups (as explained in Power Techniques).

Power Drain:
At the beginning of each new Round, the fighter who has had energy channeled into them will lose an amount of power equal to their base Power Up until they are brought down to their normal maximum Power Level.
Fusion Dance
An advanced form of Fusion, true Fusion, is achieved through a technique commonly referred to as the Fusion Dance.  A unique technique developed by a race of people called the Metamorans, the Fusion Dance allows two fighters to temporarily merge their bodies, minds, and powers into a single, powerful being.  While very few have ever actually met a Metamoran, there are numerous masters throughout the Universe that have learned, and can teach, the Fusion Dance technique.  So great is this power that numerous powerful warriors have sought out the secrets of Fusion.

The Fusion Dance is a technique that must be learned like other Power Techniques, and takes up a Z-Fighter's technique slot, and to properly perform both fighters attempting to fuse must know the Fusion Dance technique.