The user can merge two or more separate objects into one, regardless of whether the objects are organic, inorganic, living, dead, technological, etc. They can decide which parts of the objects are dominant in the union, what is deleted and which merge.
Fuse inorganic materials and create new substances with all the strengths and none of the weaknesses of their precedents.
When Hollow Ichigo (Bleach) takes full possession of Ichigo's body, the body undergoes a full transformation into a Hollow creature. He is granted with high-speed regeneration, enhanced strength, speed, durability and spiritual power, enhancing his Getsuga Tenshō, firing a Cero and having an extra appendage....
...in his new Hollow Form, he was granted with immense strength, durability, speed and spiritual power, enhancing his Cero, developed a Sonido and still has his high-speed regeneration ability...
...and later become one with Zangetsu and his Inner Hollow for the Final Getsuga Tensho.
Gogeta (Dragon Ball Z: Fusion Reborn) is a fusion between Son Goku and Vegeta.
Super Buu (Dragon Ball Z) after absorbing Piccolo, Gotenks and Son Gohan.
Super 17 (Dragon Ball GT) is a combination of Android 17 and Artificial 17.
The revived Kaguya Ōtsutsuki (Naruto) is an amalgamation of the nine tailed beasts and the Gedo statue, which became more apparent when she lost control of her powers.
Wapol (One Piece) can merge anything he eats into his own body, or spit them out as a merged being.
Cure Brighty-Bloom and Cure Windy-Egret (Precure All Stars DX2)
Cure Blossom and Cure Marine's (Precure All Stars DX2) Altered Super Forms
Precure (Precure All Stars DX3)
Dozaemon (Gintama) is the result of a piece of Gintoki Sakata's soul merging with a cat's corpse.
Sora (Kingdom Hearts series) has the ability to combine with his allies to temporarily boost his abilities with his Drive Form ability excluding the Limit Form that was introduced in the Kingdom Hearts II Final Mix version.
Kyurem (Pokémon) can combine with Zekrom to create Black Kyurem or Reshiram to create White Kyurem.
Iblis (Sonic the Hedgehog), the raw strength, merges with…
Mephiles the Dark (Sonic the Hedgehog), the mind, to form…
…Solaris (Sonic the Hedgehog)
Koume and Kotake (The Legend of Zelda) merges to form…
The Elementium Monstrosity (Warcraft) is the merging of all four Ascendant Council Members and gains new powers.