Yuga

Yuga is a character in. He is one of the game's main antagonists, alongside Hilda. He hunted the descendants of the Seven Sages as well as Princess Zelda to resurrect Ganon, and merges with him to become the Demon King himself and rule the worlds of Hyrule and Lorule.

Yuga's Hunt for Sages
Yuga is a sorcerer who has the power to become a wall drawing. With his magic wand, he can trap people within picture frames, turning them into paintings. He serves one whom he calls "Her Grace."

Yuga is first seen at the Sanctuary. He transforms sister Seres into a painting and kidnaps her, as Link can only watch helplessly. When the young hero tries to attack, Yuga swiftly turns into a drawing himself and hides in the wall, causing Link to crash into it and faint.

It is later revealed that Yuga intends to find and capture all the descendants of the original Seven Sages who sealed the Triforce in ancient times to serve his evil plans. The evil wizard then heads to the Eastern Palace, with the intention of finding Osfala, another descendant of the Seven Sages. Link follows suit, but once again arrives too late to save Osfala from being turned into a painting himself. Yuga, declaring Link an eyesore and a bother, attacks him, but the young hero soon overpowers him. Angry, Yuga casts a spell on him and turns him into a wall painting, then leaves, satisfied.

Yuga's Continuing Pursuit
Yuga then heads to Hyrule Castle, and takes over it. He sets up a magical barrier around it to prevent Sage Impa and Princess Zelda from escaping, as well as prevent anyone else from entering the castle, then leaves and wanders Hyrule in search of the remaining four descendants of the Seven Sages: Irene, Gulley, Rosso and Oren. As Link is travelling throughout the land to collect the Pendants of Virtue to obtain the legendary Master Sword, Yuga transforms the remaining sages into paintings one by one.

Yuga then went back to Hyrule Castle to capture the Sage Impa and Princess Zelda. However Link, wielding the Master Sword, broke the barrier, went inside the castle and faced Yuga for the second time. Yuga was more powerful, but was defeated again. The evil sorcerer then left to complete his ritual in another world's counterpart of Hyule Castle.

Ganon's Resurrection
Yuga then used the power of the Seven Sages to resurrect the Demon King and holder of the Triforce of Power, Ganon. Yuga then joins with Ganon, causing a combination of the two that takes on attributes and personality of both. Just when the beast was about to kill Link, a mysterious princess named Hilda came to rescue the Hero of Hyrule, using her magic to hold Yuga/Ganon at bay then teleported the hero away to keep him safe from Yuga.

Yuga was later summoned by Hilda after she attains the Triforce of Wisdom from Zelda. Hilda orders Yuga to steal the Triforce of Courage from Link, but after being beaten and asked to give the Triforce of Power to Hilda, Yuga instead steals her Triforce and engages Link once again, though he (and by extension Ganon) are defeated and destroyed.

In battle
Yuga is fought three times over the course of the game. He is first encountered as the first boss of the game in the Eastern Palace, then later as the boss of Hyrule Castle, and one last time in the two-part final battle of the game, at the end of Lorule Castle.

Eastern Palace Encounter
As the first boss battle of the game, Yuga is at his weakest in this battle. He attacks by shooting energy balls at Link, and hiding in the wall as a painting when the young hero gets too close. He is too fast to run towards him directly, so the only way to hit him to use the Bow to shoot an arrow at him. This will stun him, making him vulnerable to sword slashes or more arrows. After taking enough damage, he will get angered and become faster, and start moving along the wall in a more unpredictable way, but the strategy to defeat him remains the same. Eventually the battle will end, and Link will obtain the ability to become a drawing himself.

Hyrule Castle Encounter
As the boss of Hyrule Castle, Yuga is much more formidable. He attacks by creating two copies of himself and launching powerful spells at Link, which the young hero can avoid by standing between the pillars in the arena. Link must hit the real Yuga to stun him, making him vulnerable to more damage. If Link hits a fake Yuga, the copy will turn into a Soldier and the real Yuga will launch a powerful spell. The real Yuga ca easily be recognized by his glowing staff. When Yuga takes enough damage, he will once again become much faster and move more erratically, and his spells will have a wider range.

Lorule Castle Encounter
Now merged with Ganon, Yuga is at his most dangerous in this final battle. In the first phase of the fight, Yuga attacks in a similar way Ganon does in. He is vulnerable immediately to any attacks, but his own attacks are very powerful, and surprisingly fast. He also frequently warps around the arena, and does so more often as he takes damage. In the first stages of the fight, he attacks by thrusting his trident at Link, or slashing the young hero with it, much like a sword. Both attacks can be avoided by running out of the way fast enough, but extra caution should be taken when attempting to attack Yuga with the sword, as it will make Link more vulnerable to Yuga's slash attack. Eventually Yuga will start throwing his trident at Link, and occasionally warp out of the arena to launch energy balls from the sky. These energy balls appear immediately above Link, so the young hero must keep running to avoid them all. Eventually, the fight will end, and the second phase will begin.

In the second phase of the fight, Yuga has transformed Hilda into a painting to absorb her power and the Triforce of Wisdom, and is at his most powerful. He will initiate the fight by throwing a blue ball of energy at Link, which the young hero must reflect back at him in a game of Dead Man's Volley. Yuga will be stunned, and retreat into the wall as a painting. Zelda will then give Link the Bow of Light, so he can continue to fight. Link must merge into the wall and shoot Yuga directly with the Bow of Light. The evil beast will block the arrow and try to stop it in its track, but this exposes his back. Link must take this chance to merge out of the wall, get behind Yuga and shoot him in the back, forcing him out of the wall and rendering him vulnerable to the young hero's sword slashes. Yuga will then warp out of the arena, and cause numerous fireballs to shoot out of the walls. These fireballs will turn into bats, which Link must avoid. This strategy must be repeated twice more during the fight, but with key differences: Yuga will respond to the second arrow fired at him by charging violently and rapidly at him. Link must quickly merge out of the wall and back in to shoot him before he ends the charge. The third time around, Yuga will instantly block any arrows fired at him, and turns around too fast for Link to quickly merge behind his back. Link must in fact shoot behind him: the arrow will fly all the way across the wall and hit Yuga, forcing him out of the wall one last time and rendering him vulnerable to the finishing move.

Theory
It hasn't been officially confirmed, but it is highly likely that Yuga is Ganon or Agahnim's Lorulean counterpart, as both have red hair and greyish green skin as well as a great stature. In addition, both of them are primary antagonists and evil forces in their respective worlds. Also, each person's Lorulean counterpart seems to be identical in certain aspects but completely diferent in other aspects. In Yuga's case, the difference would be in power: Yuga has to rely on his magic staff, and is powerless without it, unlike Ganon, whose power comes from himself and the Triforce of Power.

Trivia

 * Yuga's name is derived from the Kanji 油画/Yuga, which is Japanese for oil paintings, a reference to his magical abilities.
 * The weapon wielded by Yuga when he is merged with Ganon appears to be a combined version of the Trident and Yuga's paint brush staff.