Wall Merging

Wall merging is an ability in The Legend of Zelda: A Link Between Worlds.

Yuga's Ability
The Lorulean sorcerer Yuga has the ability to transform himself into two-dimensional paintings, merging into walls to evade enemy attacks. He also has the ability to inflict this on other people and creatures; however, other characters afflicted by his magic are normally incapable of acting on their own.

This ability is first seen in the Sanctuary, wherein Yuga transforms Seres into a framed portrait to take with him after imprisoning the guard captain on a wall; when Link attempts to attack him, Yuga merges into the back wall of the Sanctuary, unaffected by Link's attack. He later uses his magic to imprison Osfala, and during the following battle with Link, Yuga periodically merges into the wall in order to avoid Link's attacks. After the battle, Yuga attempts to dispose of Link by imprisoning him within the wall as well, though this does not last as with the captain.

While Link is collecting the Pendants of Virtue, Yuga continues to imprison the other Sages in framed portraits. When Link confronts Yuga in Hyrule Castle, Yuga imprisons Princess Zelda in a portrait with the others; once this has been done, he fights Link once more, creating copies of himself that are capable of merging into walls as he is.

After Yuga combines with Ganon, he retains his ability to merge into walls, using it during the final battle.

Link's Ability
After Link is imprisoned in the wall of the Eastern Palace following his battle with Yuga, Ravio's Bracelet frees him from the imprisonment. From then on, the charm allows him to move within walls, much like Yuga can. However, Link is unable to take others into or out of the walls with him.

When Link is in this two-dimensional form, he is unaffected by enemies and hazards, remains at the same height on the wall as when he entered the, and can slip around otherwise impassable corners and even in between iron bars, making it largely a puzzle-solving mechanic. Link can also collect items that are drawn on the walls (like Recovery Hearts and Rupees), and he can detach Baby Maiamais from walls by exiting behind them. However, when Link is in this form, the gauge on the left side of the screen slowly drains, acting as a timer before Link must return to his normal form.

During the game, Hyrule and Lorule are joined by special portal cracks scattered throughout the two kingdom. Link is thus able to travel between the two kingdoms by entering these cracks while he is a drawing.

Trivia

 * Link's appearance as a drawing resembles the illustrations of the Hero of Time from the prologue of ; it also bears a resemblance to ancient Egyptian hieroglyphs.