|“||Soon, Dream Land will be wrapped around my knitting needles!”|
|— Yin-Yarn • Kirby's Epic Yarn|
Yin-Yarn is the main antagonist and final boss of Kirby's Epic Yarn and its remake, Kirby's Extra Epic Yarn. He shares the name of the stage he appears in, which follows Castle Dedede and preceeds Meta Melon Isle. He can manipulate most things made of yarn with his pair of wooden knitting needles, which are held in each of his hands. Yin-Yarn's true origins and motives are never revealed throughout the course of the game, and he comes across as a land-hungry villain ultimately seeking control of Dream Land, although he confesses himself that he is not sure what to do with it.
Yin-Yarn is entirely made out of yarn with the exception of his nose. His yarn appearance could be attributed to his origin from Patch Land, or because he transformed himself using his Metamato. Yin-Yarn's unnamed knitting needles have purple and yellow eyes, and (coincidentally) Yin-Yarn's possessed victims' eyes flash between yellow and purple. The needles are Yin-Yarn's apparent source of power, and they are later revealed to be independent of Yin-Yarn and have a mind of their own, and they could well be Yin-Yarn's creator and the true masterminds behind Yin-Yarn's actions.
Yin-Yarn is a yarn sorcerer with a black moustache, a large button for a nose, two purple pupils and an orange body with bright orange stripes. He wears a green hat with a yellow band, and wields two knitting needles, one with yellow eyes and a single horn, and the other with purple eyes and two horns that frowns. These knitting needles may be his life essence or controllers. He wears the stolen sock around his neck.
His Mega form is a round robot similar in appearance to Kirby's Tankbot form. He has his then-enlarged knitting needles, his hat, even more evil facial features, and bladed wheels for feet.
- For the story of Kirby's Epic Yarn, see Kirby's Epic Yarn.
The story begins with Yin-Yarn wreaking havoc in both Patch Land and Dream Land, but Yin-Yarn's work in Patch Land was already done. He unleashed yarn monsters all over Patch Land, stole one of a pair of magical socks, and unraveled the pieces of magic yarn holding Patch Land together, splitting it into seven pieces. He used the magic yarn to create bosses to stop heroes from reuniting Patch Land. As Prince Fluff later explains, the magical socks function as portals to each other, but with Patch Land in pieces, that power is lost. Yin-Yarn's sock now transports his victims directly into Patch Land, which he controls, and turns them into yarn in the process, and Kirby became his first victim.
Yin-Yarn did all this in Patch Land so he could suck in the residents of Dream Land and make them work for him later, and it allows him to take over Dream Land with little effort. How Yin-Yarn got to Dream Land in the first place is not explained. He removed King Dedede from his castle and Meta Knight from Halberd, controls their minds, and uses them to stop Kirby and Prince Fluff from reuniting Patch Land, which allows them to go to Dream Land and get to him. By the time Meta Knight became his victim, Dream Land is already made of yarn.
After the fight with one possessed Meta Knight, Kirby is saddened by King Dedede's account of Yin-Yarn taking over Dream Land, but with Patch Land fully restored, the magical socks regained their original power. Kirby, Prince Fluff, Meta Knight (now recovered) and King Dedede go into the remaining sock in Patch Castle in order to confront Yin-Yarn directly, but with Dream Land under his control, Yin-Yarn has already discarded his magical sock, so the heroes end up on a sock in a grassy yarn field instead. They eventually find Yin-Yarn anyway, and Kirby and Prince Fluff confront him in a final showdown.
Kirby and Prince Fluff succeed in unraveling Yin-Yarn, and proceed to do the Kirby Dance, but they are interrupted when Yin-Yarn's knitting needles come to life and create Mega Yin-Yarn from Yin-Yarn's magic yarn to stop them. Meta Knight flies over all of them and drops a metamortex, giving Kirby and Prince Fluff their Tankbot form, and they proceed to decimate Mega Yin-Yarn. Kirby and Prince Fluff revert to normal after passing a reel gate, trap the scared knitting needles between them, toss them to Patch Land (possibly their place of origin), and finally finish the Kirby Dance.
Dream Land shortly reverts to normal and the ending sequence plays.
Initially, Yin-Yarn re-knits Fangora to stop Kirby and Prince Fluff, and then Capamari's second form, along with his Octopeas. Both bosses only require a single hit to defeat, and the strategies remain the same as before.
Right after the defeat of each boss he created, Yin-Yarn drops a curtain in front of Kirby with a single door at the top, and sends endless Soochers in set patterns behind the screen to try and hurt the heroes. The heroes can jump on the stitching left by the Soochers and reach the door above to get in front of Yin-Yarn's curtain and end the sequence.
Yin-Yarn later removes sections of the floor and sends in Scarfies, Buttonbees, Bow Waddle Dees, Uniclods, Chillys, and even Big Waddle Dees in an attempt to knock Kirby and Prince Fluff off, but the heroes can make yarn balls out of most of these and toss them at Yin-Yarn, which brings him to the ground and exposes his weak spot (a large button) to attack.
|See also: Mega Yin-Yarn|
Yin-Yarn's name is a pun on Yin-Yang.
- His battle theme is a remix of the boss theme and Miracle Matter's theme from Kirby 64: The Crystal Shards. In the final phase of the fight, the tempo increases even further.
- During the battle there is a swirling black mass in the background. In the mass, one can see the Halberd, Meta Melon Isle, and Patch Castle, among other things. This is the case even if the player has not unlocked the two bonus levels, Battleship Halberd and Meta Melon Isle.
- Yin-Yarn is the only final boss in the Kirby series so far to have facial hair.
- Yin-Yarn is one of the three final bosses to resurrect previous bosses, the others being Necrodeus and Drawcia. However, Drawcia does not resurrect bosses during the final battle, but during several events of the game.
- Just like Drawcia, Yin-Yarn transforms Kirby’s world, as well as Kirby's design and battle style.
- Yin-Yarn does not directly attack in his first form; all of his attacks consist of resurrecting bosses or summoning enemies to attack Kirby.
- Yin-Yarn appears as a collectible keychain in Kirby: Triple Deluxe.
- Yin-Yarn and Void Soul are the only bosses in the main Kirby series to flood the arena with liquid.