Mother Hydra

"'I cannot think of the deep sea without shuddering at the nameless things that may at this very moment be crawling and floundering on its slimy bed, worshipping their ancient stone idols and carving their own detestable likeness on submarine obelisks of water-soaked granite.'""H. P. Lovecraft, Dagon, 1917"Mother Hydra is the consort of Father Dagon. She rules from the underwater city of Y'ha-nthlei and is one of the two monarch ruling over the Deep Ones. She is also the final boss of Dark Corners of the Earth.

Appearance
Hydra's appearance in game is that of a collosal fat female humanoid similar to the Deep Ones. She has four digits on her limbs and two sets of breasts. When first encountered by Jack, it is possible for him to lose sanity, but after the first flow of water is released, Jack will calm down.

Role in the Mythos
The consort of Dagon, Mother Hydra rules the Deep One race at his side and is worshipped by her children and their affiliated cults, such as the Esoteric Order of Dagon. She, along with Great Cthulhu and Dagon forms the "Holy Trinity" of her race. Mother Hydra, along with Dagon and the Deep Ones, is also said to have been assigned by Great Cthulhu himself the guardianship of his "daughter".

There is debate as to whether or not Dagon and Hydra are lesser Great Old Ones or mere grotesquely mutated Deep Ones. Therefore, although considered deities, they are typically not classified as Great Old Ones. Since Deep Ones tend to grow as they age, the former is possible.

Strategy
To defeat Hydra, you first have to activate the drains at the back of the boss area. However, you cannot reach them as Jack cannot jump high enough. But if you were, let's say, a Deep One, maybe you could.

Fortunatly, there is some kind of plate Jack can interact with to meditate and enter a Deep One's body. However, Hydra's chanting prevents you from doing this, as Jack "cannot concentrate" properly as long as he hears it.

To remedy this, go back to the golden gong in the Temple entrance and hit it point blank with a fully  charged shot from the alien gun. This will cause a long deafning sound. During this, make your way back to Hydra, killing any Deep Ones you meet along the way. Stand in the pool of water in front of Hydra and wait for the deafness to be over.

You are then transported into the mind of a Deep One. Find the other drains at the back (they are high up, which makes it impossible to reach them in a human body) and activate the drains. Every time you activate a drain, you lose control of a Deep One and will have to kill it. Be aware that Hydra will summon another pack of her children once in a while, so be careful not to run out of ammo. Repeat the gong strategy until all three drains are activated. To finally kill Hydra, shoot a charged shot from the electricity gun into the pool you were standing in.

Role in the game
Just like Dagon, Hydra is often referenced in the incantation "Ia Hydra" uttered by the cultists. She is seen inside her Temple in Y'ha-nthlei leading prayer with her fellow cultists, protected in some kind of bubble. Her wailing stops Jack from defeating the Deep Ones, but he eventually kills her using the Yithian power weapon to electrify the water leading underneath her barrier. Killing her destroys the shield around the city, allowing the Navy submarines to bombard the city.

However, just like her consort, if Hydra truly is a Great Old One, then she is likely to have survived her defeat.

Trivia

 * Hydra has never appeared in person in any story of the Cthulhu Mythos, being only referred to in Lovecraft's story The Shadow Over Insmouth.
 * One should not confuse Mother Hydra with another creature of the Cthulhu Mythos also named Hydra from the pamphlet On the Sending Out of the Soul.
 * Jarred W. Wallace penned a mock nursery rhymes book named after Hydra, titled  Mother Hydra's Mythos Rhymes .