Xurkitree absorbing electricity from the ground in its tree-like state
Xurkitree is a very tall Ultra Beast that resembles a vaguely humanoid mass of electrical wiring. Its "head" is a white, brightly glowing electric spark with numerous points and no visible face. Below its head is a mass of black cables for its torso and limbs; there are white bands resembling zip ties throughout its body as well. Its arms have ties where its shoulders, elbows, and wrists would be. The upper arms have two cables, while the lower have three. At the ends of its arms are copper structures that resemble hands, each with six flat "fingers". The legs have ties at the hips, knees, and ankles and are composed of four cables fused together for the whole length. The feet have four toes possessing "claws" of exposed copper; each foot has two fused toes pointing forward and two separate toes pointing backward. Finally, its tail has three ties and four cables, one of them loose in two sections. The tail ends in what resembles a three-pronged plug. It is the tallest Electric-type Pokémon.
Xurkitree live in another world named Ultra Plant. There, many have been seen unmoving, with their arms and legs stuck to the ground, similar to trees as they absorb electricity from the ground. Xurkitree vary greatly in size, from being a little bigger than a human to being the size of a mountain. Because this Ultra Beast reportedly raided a power plant, it is speculated to sustain itself with electricity. Witnesses claim that its entire body crackles with astonishing electrical power. According to Wicke from the Aether Foundation, Xurkitree's most distinctive feature is an organ that can generate power. This UB's bodily makeup is highly reminiscent of electric wiring, thus enabling it to conduct electricity with great efficiency.
It can discharge as much as a million volts of power at a time. When it begins to run out of power, it stabs its legs and tail into the soil, entering a treelike state as it absorbs electricity from the ground.
Wicke also claims that like all Ultra Beasts, Xurkitree stores the same energy possessed by Totem Pokémon within its body, which takes the form of a red, flaring aura[1]. This energy is called Z-Power. Xurkitree and Blacephalon have a rivalry with each other, often completing in contests to see who can shine the brightest as depicted in Twirling with a Bang!.
Xurkitree debuted in Twirling with a Bang!, where it first emerged from an Ultra Wormhole on Melemele Island. The next day, the Ultra Guardians set out to return it home, only for it to wind up clashing with a Blacephalon. After distracting both Xurkitree and Blacephalon, the Ultra Guardians managed to weaken and catch both Pokémon at the same time, allowing them to be sent back home. It reappeared in a flashback in Securing the Future!.
Xurkitree is the Glowing Pokémon, and as you can tell by the look, it's an Electric type that unleashes powerful electric shocks using stored electricity.
GOTCHA!
A Xurkitree briefly appeared as a silhouette in GOTCHA!.
In Pokémon Sun and Moon, Xurkitree has a catch rate of 30 and a base experience yield of 114.
Origin
Xurkitree appears to be based on sparking electrical wires and power-lines. The three prongs on the end of its tail resemble a power plug, while its long "fingers" resemble copper wiring. Its design also shares some small aspects of a tree, especially Christmas trees; its head resembles a Moravian star or a tree-topper, while the white bands on its limbs may be based on fairy lights, though they could also refer to cable ties, which are used to hold multiple cables together.
The design of Xurkitree may also be based on a visual pun of the term "live wire"; as in "a wire carrying an electric current" and "a wire that is literally alive".
Name origin
Xurkitree may be a combination of a corruption of circuitry and tree.
Denjyumoku may be a combination of 電気 denki (electricity) or 電磁 denji (electromagnetism) and 樹木 jumoku (tree).
↑Wicke, Pokémon Sun and Moon:"When the UBs pass through the Ultra Wormhole, they are bathed in a great deal of this energy and likely store it within their bodies."