Cubus Sisters

The Diabolical Cubus Sisters, also simply known as the Cubus Sisters or House of Cubus are a group of four paranormal sisters who act as a group boss in The Legend of Zelda: Phantom Hourglass. In both appearance and role, they resemble the Poe Sisters from previous games. They act very childish, give Link bad advice on multiple occasions, and seem to harbor an intense fear of spiders, though this may simply be part of their "game." Their name comes from and, two similar types of demon generally representing lust, and sometimes shown using human-like and monstrous forms separately, much like the Cubus Sisters themselves.

When Link first boards the Ghost Ship, the Cubus Sisters are disguised in humanoid forms, but continually act suspiciously and demonstrably lie on multiple occasions. After defeating a group of Poes, Link meets the youngest sister, with a red hood, who recognizes Link on sight. She claims the Cubus family were simply innocents who were swept up by the Ghost Ship, and asks Link to reunite her elder sisters with her, telling him Tetra may be with one of them. She also warns Link of the Reaplings, describing them as the "fallen" in rapid repetition. Link finds the second youngest one, dressed in blue, a short distance away. Link must escort her back to the first, making sure to keep her nearby. If he gets too far away or gets too close to a Skulltula for more than a split second, she will freeze up and start cowering, also screaming in the latter case. To get her moving again, Link needs to speak with her. Once Link reunites the two, the youngest expresses disappointment at Link not finding Tetra, but asks Link to continue looking, while they stay in the room and apparently eat candy.

Link finds the second oldest, dressed in yellow, past a maze with a Reapling in it. Once rescued, she tells Link of two Treasure Chests nearby, telling him to pick the one on the left. If he claims to not know which one is left, she tells him that it's the one that "isn't right." In fact, the left chest contains a Rupoor for 10 Rupees and triggers a trap spawning another Reapling. If she screams, this also alerts nearby Reaplings. Once she is returned, the three tell Link that the eldest sister is the most cowardly of all of them, and as such tends to hide in barrels, making the cargo hold a likely location as it is filled with steel drums. This is indeed correct, as the eldest, wearing turquoise, is found under a drum in that location. After Link finds him, she warns Link not to shoot arrows into the Reaplings' backs so as to not anger them; in reality, shooting the eye in their backs temporarily stuns them.

Once Link has reunited all four, they decide to have some "family time." They admonish Link for not playing along with their "game," as he was supposed to be literally scared to death by the Reaplings. They then tell him that they will now "play rough" with him, as they had done with Tetra. They take him to the foredeck, telling him that to save Tetra, he needs to play a match of "dead man's volley." They then become their true, ghastly forms, flying to the upper screen.

For the first phase, the elder three fire laser beams while moving around slowly, while the youngest fires a projectile that must be returned with the sword. If it is not, it splits into three and travels across the field in different directions. After returning her volleys twice, the sister is defeated. For the second phase, the second oldest now fires projectiles while the others shoot lasers. She can also shoot arrays of small four balls that cannot be blocked, based on those of Agahnim. Now when returned, the sisters will bounce the ball between each other and back to Link. Through this, the second youngest is hit twice and defeated. In the third phase, the second oldest now fires a laser while the eldest shoots projectiles. They again bounce returned projectiles, though now it hits them variably, leaving them at two for longer. First the elder is hit, then the younger, then the younger again, defeating her. For the final stage, the eldest fires three projectiles at once, with two being non-returnable and one being returnable. Due to no longer having any sisters to bounce it between, she now returns it to Link at an angle, increasing in speed while slowly getting closer to narrow the gap. After three more hits, she is defeated. She congratulates Link for his skill at the game, telling him that she would reward him if they had any trophies. She tells him instead to "drag that precious Tetra off" with him, disappearing into the Ghost Key while wishing him a drawn out goodbye. A chest with a Heart Container and a portal leading back to the room they reunited in then appear.

Trivia

 * The concept of leading a suspicious girl through a dungeon only for her to turn out to be the boss may have been inspired by Blind the Thief in The Legend of Zelda: A Link to the Past.
 * If the Heart Container is not taken, it will be mailed to Link by someone claiming to be watching him "from above." This is to avoid it becoming permanently missable, since the Ghost Ship vanishes after Tetra is recovered from it.