Abyssal Leviathan: Tentalus (古代海獣 ダイダゴス Kodai Kaijū Daidagosu?, Ancient Marine Monster: Daidagos) is the boss of the Sandship, the fifth dungeon in The Legend of Zelda: Skyward Sword. It resembles an anthropomorphic sea monster.
Right after Link inserts the Squid Carving into the lock and enters the control room, Tentalus attacks the ship, blocking the corridors with its tentacles. Link must use a Skyward Strike to sever these tentacles as he makes his way to the deck to face Tentalus. The tentacles can also be removed with Bombs. As he makes his way through the corridors of the ship, Link must avoid getting hit by rolling Barrels, which he can either dodge or destroy with his sword. If Link gets too close to any wiggling tentacles, they will grab him and he must break free before they pull him out. If he is pulled out, Link will respawn in a nearby location. As Link progresses towards the ship's exterior, the lower levels will begin to flood with water. When Link reaches the outside, the door collapses behind him, and the battle begins.
Tentalus starts off by diving underwater and attacking Link by breaking through the deck from below with its tentacles. If one of the tentacles grabs Link, he must quickly break free or it will throw him off the ship. To draw Tentalus out, Link must destroy a number of tentacles with a horizontal Skyward Strike, a fully charged shot from the bow, or a bomb. Once enough tentacles have been destroyed, Tentalus will rise and assault Link directly by slamming its arms down on him. In order to stun the beast, an arrow must be shot into its enormous eye, causing Tentalus to fall upon the ship so that Link may strike it with his sword. While a proficient marksman can hit Tentalus as soon as it opens its eye, it is easiest for Link either just after Tentalus slams one of its arms down, or after Link severs one of the arms with a Skyward Strike. While it is stunned Link can also cut the dreadlock-like tentacles on its head to obtain recovery hearts. After taking enough damage, Tentalus will start destroying parts of the ship, and Link must rise to the higher part while avoiding rolling barrels to initiate the final phase of the battle.
In the final phase of the battle, Tentalus will attack Link with the tentacles on its head, which have grown mouths and attempt to bite him. Link must cut the attacking tentacles, which will quickly regenerate, then fire an arrow at Tentalus' eye when it stops to roar. Tentalus will fall over once again, and Link can attack as he did before. After taking enough damage in this manner, Tentalus will be defeated.
There also is a bug when fighting Tentalus. Once Link hits Tentalus' eye once with the bow to knock him out, if Link keeps hitting it's eye with arrows, the battle will be stuck in the first phase.
| “As you can likely gather from its other title, this "Abyssal Leviathan" is said to have been a tyrant of the ancient seas. Its enormous tentacles can be repelled but they will regenerate after a short time.
My analysis shows that by repelling a number of its aggressive tentacles the beast will reveal itself. There is a 99% probability that the tentalces that attacked you on the ship, Master, can be attributed to Tentalus. I theorize that using sacred power will be the most effective means of repelling the tentacles.
Results from my analysis confirm that its tentacles can be severed with a well-aimed Skyward Strike. I theorize that the creature's eye is its weak point, but the probability that you can actually hit the eye with a Skyward Strike is approximately 0%. Instead, I recommend utilizing long-rang weapons.
T accurately strike at the creature's eye--its weak spot--a bow will be most effective. You can press control stick to move with your bow drawn. I recommend shooting arrows immediately after dodging attacks launched by Tentalus.
In order to attack Tentalus's weak spot, its eye, you must first deal with the tentacles attempting to latch on to you. My analysis shows you can easily slice the tip of the tentacles with your sword.
Because this monster's tentacles attack incessantly and in large number, it is too dangerous to respond to them one at a time. My analysis indicates it is possible to repel the tentacles more effectively by concentrating an all-out assault on them with your sword. When the tentacles are repelled they may drop hearts and arrows. Should you find yourself in danger because of low hearts or arrows, concentrate on attacking the tentacles rather than fleeing from battle.”
Tentalus is possibly a portmanteau of "tentacle", referring to its many appendages, and "Tantalus", an ancient Greek mythological figure who was doomed to live in a cave with a pool of water and a grape tree above him. Tantalus was unable to drink from the pool or eat from the tree as a form of eternal punishment for his wrongdoings.