Giant Snake-Tailed Chameleon

This summon is a large chimera-like chameleon with snake for a tail. Like all of Nagato's summons, it has a number of body piercings and Rinnegan, implying that it is being controlled.

Abilities
Much like a real-life chameleon, this creature can also blend with its surroundings for camouflage, so perfectly that it renders itself completely invisible to other viewers around. This ability has been used by the Animal Path of Pain to step inside the chameleon's mouth and attack his opponents by surprise. As perfect as it may be, however, this camouflage can be detected by barrier-related techniques, as when Jiraiya tried to use his Barrier: Canopy Method Formation to locate it, Pain had the chameleon distance itself from him, and attacked him with an offensive summon. Another reptilian trait that the chameleon shows is the ability to crawl on vertical and inclined surfaces, such as walls. Also, it has exhibited great destruction capabilities, as it could fend off attacks from Konoha ninja and wreck houses and buildings during the invasion of Pain. The snake-tail can be used as a prehensile limb, to be able to grab and capture intended targets for Pain with its tongue, as shown during the Fourth Shinobi World War.

Itachi Pursuit Arc
It is first summoned during Pain's battle with Jiraiya in Amegakure, swallowing Pain's Animal path and turning invisible via camouflage, to conceal the latter and give it stealth-based advantages. After failing to detect it via a barrier technique, Jiraiya summons Shima and Fukasaku to use Sage Mode. Analysing the situation, Shima is easily able deduce the creature's location and restrain it with her Fighting Tongue Bind technique, before excreting a corrosive liquid along her tongue's length to disable it's camouflage. Fukasaku then slices the creature in half, with the Fighting Tongue Slash.

Invasion of Pain Arc
In the anime, the chameleon is summoned again by the second Animal Path during the invasion of Konoha. After causing a rampage along with Pain's other summons, it is de-summoned (along with other animal summons) when Pain decides to concentrate his power solely to the Deva Path for a large-scale Shinra Tensei on Konoha.

Shinobi World War Arc
During the Fourth Shinobi World War, the chameleon is summoned by Nagato, who has been reincarnated by Kabuto Yakushi. Nagato, being controlled by Kabuto, uses it to hide within it's mouth, while the creature is invisible, and then unleash a massive Shinra Tensei on his surroundings to obliterate a portion of the forest while battling Naruto Uzumaki and Killer B. After Nagato revitalises to his youthful appearance by absorbing B's chakra, he has the chameleon use his snake-tail to hold Naruto while he removes his soul. However, both it and the King of Hell get blinded when Itachi throws several kunai into their eyes, allowing him to save both Naruto and B from Nagato.

Trivia

 * In the manga, when the chameleon is seen in chapter 374, the snake had regular eyes. This was corrected in subsequent chapters and the snake was seen with Rinnegan eyes.
 * The same error was made in chapters 550 and 551.