I have this headcanon about the Dark Link mini-boss room in the Water temple.
What if, as some kind of test in the Water Temple, the mini-boss room presents some kind of Dark version of yourself before you can progress in the temple? Like some kind of are you worthy thing.
Obviously, for Link, it would be an evil version of him, that has all the skill he has and his main weapon, but for, say, anyone else, it be an evil version of them, with their most valuble asset. Like, if it was Ami (oh, what the heck, this is mainly a Sailor Moon forum) It would be dark Sailor Mercury (which already happened in PGSM... oh well) and she'd challenge her to a chess match or something. But, as with Dark Link, instead of using his main weapon, the Master Sword, you have to use the Biggoron's sword, the Megaton Hammer, or Din's fire (you can use the Master sword but's REALLY difficult). So Ami, in this fictitious situation, would just have to attack her and Dark Mercury couldn't do anything. And the whole point of this room is to humble you so you don't become overly confident in your abilities. Because everyone has weaknesses.
So this is my rambling. If it doesn't make any sense, then I'm sorry.

Well in Zelda II Dark Link appears after the boss Thunderbird. Occurring to Zelda Wiki it's a test before Link can obtain the Tirforce of Courage and walking Princess Zelda.

Yeah this posg was really just a random thought of mine. It's unfortunate thatDark Link only really made an apearance in those two games as a boss though.

Dark Link has been in other games:

Zelda Wiki:

Quote :

The Adventure of Link:
In his first appearance in the series, Dark Link is known as Link's Shadow and appears as the final boss after Link defeats Thunderbird in the Great Palace.^[3] He serves as the final test before Link can obtain the Triforce of Courage and wake Princess Zelda. Link's Shadow is the most difficult opponent to appear during Link's second quest to save Hyrule.
The strategy for Link's Shadow is to attack him where his guard is down. Another strategy that many mistake for a glitch is to duck in the very left corner of the arena and repeatedly stab when he gets close.
Dark Link's appearances in Event Matches during Super Smash Bros. Melee and Super Smash Bros. Brawl are largely based upon this battle. This battle also formed the basis of the Streetpass Battle Mode of A Link Between Worlds, marking the first time that music from The Adventure of Link returned to use in another Zelda game.

Ocarina of Time

Link confronts Dark Link in the Water Temple

In Ocarina of Time, Dark Link appears as a mini-boss in the Water Temple, where he materializes from Link's reflection in the water to confront his good counterpart. Dark Link reacts to most of Link's movements and attacks, usually defending himself in the process.^[4] Dark Link has the same amount of health as Link; the number of Heart Containers the hero has equals the number of hits with the Master Sword it takes to defeat his doppelganger. When hit, Dark Link will fall through the floor and spring back up afterwards. At the beginning of the battle, Dark Link is nearly transparent, but will gradually become opaque as the battle progresses. When he is fully opaque, he will become more aggressive and actively attack Link instead of simply reacting to his moves.
There are a variety of strategies to defeating Dark Link. Link can use either Megaton Hammer, the Deku Nuts, or the Biggoron Sword, or by using his sword and while L/Z targeting him do a horizontal slash on the opposite side of his shield, which gives Link an instant hit. Stocking up on magic potions and using Din's Fire is another option that makes the fight against Dark Link very easy. Din's Fire is one of the best options in both the passive and aggressive part of the battle, as it will cause damage every time, provided that Dark Link is in range. If Link performs a sword thrust, Dark Link will simply hop on to the blade of the sword before attacking (if aggressive). Once Dark Link is defeated, Link is able to continue on to a room containing the Longshot.^[5]
Dark Link shares Link's voice, but it is heavily distorted, giving it a demonic feel.

Oracle of Ages

During the second phase of the final battle, Veran creates four clones of Dark Link that mimic Link's movement in reverse and act as dangerous obstacles. Unlike other appearances of Dark Link, these clones do not attack, and are useful in recovering health, as they are easily destroyed and drop one Heart each. They are similar in behavior to Arm-Mimics andMask-Mimics.

A Link to the Past

In the Game Boy Advance port, after completing both A Link to the Past and the multiplayer Four Swords game, the Palace of the Four Sword is unlocked. The Dungeon Master is four Dark Links, each with a unique tunic, corresponding to the colors of the Links that hold the Four Sword. Reaching the final room of the dungeon causes the four different colored Four Swords to rise into the air, and following this the Dark Links will drop from above. Each Dark Link has slightly different abilities, but they all aggressively attack with sword swipes and do not open their defenses often. They are quite agile, able to leap backwards out of the way of Link's attacks. They are fought one at a time, and they get progressively more difficult. The green Dark Link uses the Pegasus Boots to suddenly dash at Link; the red Dark Link uses the Hurricane Spin and the Pegasus Boots. The blue Dark Link also uses Pegasus Boots and the Hurricane Spin, and he can leap into the air to perform aDown Thrust (this is also similar to Link's use of the Quake Medallion). The purple Dark Link is the final Dark Link, and utilizes the Pegasus Boots, Hurricane Spin, Down Thrust, and the Sword Beam. Defeating each Dark Link will break the curse on the Four Sword and return it to normal.

Twilight Princess

Dark Link makes a cameo appearance during a cut-scene in Twilight Princess that tells the tale of how the Twili race was banished to the Twilight Realm. Portraying the powerful Dark Interlopers who sought to control the Sacred Realm, three clones of Dark Link manage to destroy Link (portraying a common citizen) before they are banished to the Twilight Realm by theLight Spirits.

Spirit Tracks

Dark Link appears as the final challenge of the Take 'Em All On! mini-game in Castle Town. In this appearance, he attacks using a blade as dark as himself, that subsequently leaves a fitting black trail, and he can also place bombs and shoot arrows. He can also perform a jump attack like Link, only his is higher and much slower. Dark Link also mimics Link's sword attacks when he himself is not attacking, so Link must block his attacks and then counterattack. The music played when fighting him is the same as the track used whenLink chased the Ghost Ship during the final boss's second phase in Phantom Hourglass. Conversely to his appearance in Ocarina of Time, he slowly fades from a pure black to a translucent gray as he takes damage, and once defeated, he falls over on his back and disappears, his eyes eerily left open during the whole animation. The room he is fought in is the only one which contains Hearts, despite Joynas's earlier warning that there is no way to recover health in the challenge rooms.^[6]

Well, as a main boss more or less. I think he should have been the main boss of the Water Temple, I disliked Morpha.