It is more of an assimilation (the alternate title of this type of fusion) than fusion, as one Namekian absorbs the energy, strength, memories, and intelligence or thought pattern of another. Both participants must willingly consent to fuse in this manner and usually the pair agrees to the stronger of the two to serve their body as the host; the reason for this consent is that the body of the absorbed Namekian disappears during this fusion and the consciousness ceases to exist as a body. The agreed host places his hand over the chest of the other one and through unknown thoughts, a flash merges them. After the fusion, the non-host's consciousness lives inside the body of the host from this point onwards and their life span as a body ends. The host's consciousness dominates the body, while the non-host serves to aid him by supplying information, thereby meaning that the absorbed consciousness remains separate from the host's. It is also possible to merge with more than two Namekians. There doesn't appear to be a limit in how many Namekians can fuse into a single being, Saonel and Pirina having fused with a large but undetermined number of fellow Namekians from Universe 6. It's unknown if the mentioned Namekians, already being the product of a large number of fusions, could fuse together.
This technique is used twice in the Dragon Ball Z manga and anime; in both cases Piccolo takes the role of the absorber. The first time, he fuses with Nail, the last Warrior-type Namekian, before fighting Frieza, while in the second time, he fuses with Kami before fighting Imperfect Cell in Gingertown. Because Kami loses his body after the fusion, the Dragon Balls turn to stone and the Black Star Dragon Balls were restored as well as the Nameless Namekian essentially became whole again through Piccolo's fusion with Kami. On both occasions, the new Piccolo is strong enough to match or possibly beat the current villain.
The technique returns during the Universe Survival Saga, with Universe 6's Saonel and Pirina fusing with many of their fellow Namekians so they would be strong enough to be a part of Team Universe 6. Because of the larger number of Namekians absorbed, the two weren't able to use all of their newfound power until their fusions stabilized most of the way through the tournament, which resulted in their gaining a massive power boost while fighting Gohan and Piccolo.
The largest difference with this type is that once fused it cannot be undone. Both the host and his partner maintain separate consciousnesses: while the host has control of the body, the partner can watch from inside and is capable of speaking with the host's consent; during his fight with Imperfect Cell, Piccolo gives Kami credit for coming up with the idea of playing possum in order to extract information from Cell.
The resulting fusion causes a massive power boost; prior to fusing with Kami, Piccolo (who had trained for the arrival of the Androids and had fused with Nail) had fallen from one punch to the stomach by Android 17. However, after fusing with Kami, Piccolo is able to even the odds and even overpower the Android at times.
In the Tournament of Power, the two Namekians from Universe 6, Saonel and Pilina, both state they previously fused with several Namekians from their homeplanet in order to drastically power up and increase their chances of success in the tournament.
Appearances in games
In the Budokai series, this technique is used by Piccolo under the names Sync with Nail and Fuse with Kami.
In Dragon Ball Z: Supersonic Warriors, Piccolo absorbs King Piccolo (making him truly complete), and the absorption is enough to increase his strength to the point of being an equal with Super Buu. In the arcade game Dragon Ball Heroes, the Namekians, including players' avatars, have the ability to use this technique.
Through the card "Namekian Fusion", any Namekian can fuse with any other in the Collectible Card Game. The Namekians in this game include Piccolo, King Piccolo, Dende, Kami, Nail, and Guru. Lord Slug is also featured in the game but he is classed as "Super Namekian", and cannot use the cards effects as such.`
In Dragon Ball: Xenoverse, Percel mentions going to a timeline where King Piccolo has absorbed Kami and his Super Namek strength allows him to give birth to Mutated Namekians capable of waging war against both the Red Ribbon Androids and Babidi's forces.
- Piccolo + Nail and Kami = [Piccolo's body]
- Saonel + Several Namekians from Universe 6 = [Saonel's body]
- Pilina + Several Namekians from Universe 6 = [Pilina's body]
- Piccolo + Maima & Tsumuri (& Dende) = [Piccolo's body] (Super Saiya Densetsu)
- King Piccolo + Kami = [King Piccolo's body] (Altered timeline; Dragon Ball: Xenoverse)
- Piccolo + King Piccolo = [Piccolo's Body] (Supersonic Warriors)
- Namekian avatar + Piccolo = [Namekian avatar's body] (Heroes)
- Any Namekian in the Collectible Card Game = [Any of the Namekian's bodies]