Squirk

Squirk was the main antagonist of the Generation 1 My Little Pony episode "The Ghost of Paradise Estate" - he was a giant, vaguely humanoid octopus that once ruled an underwater kingdom when much of the world was under the ocean.

Personality
Squirk was a horrible ruler, a tyrant who reveled in cruelty - utilizing the magic of the Flashstone amulet he amused himself with senseless acts of villainy and earned much hatred and fear from those who suffered under his rule.

Squirk would remain the unjust ruler of the underwater world until eventually the ocean began to fade away as Dream Valley began to take form - at this point magical birds known as the Pannas arrived looking for a new home.

Biography
Squirk didn't want to share his land with the Pannas and rose from the depths to terrorize them with the Flashstone but their leader refused to allow Squirk to bully him into leaving and fought the monster - taking the Flashstone amulet and shattering it into two pieces.

One half was thrown into the deepest ocean and the other was tossed to what would later become Paradise Estate, Squirk retreated into the ocean but refused to come out until his enemy had grown old and weak, Squirk was immortal and thus knew better than to risk another fight until the odds were in his favor.

Sure enough in time the Pannas leader grew old and Squirk abducted him, forcing his granddaughter Pluma to go to Paradise Estate to retrieve the first half of the Flashstone amulet as well as scare away the Little Ponies who now called it home.

Pluma retrieves half of the Flashstone by destroying Paradise Estate and capturing the Little Ponies - however she feels remorse over what she is doing (albeit by force) and tries to use the amulet to undo the damage, but only half of Paradise Estate is restored.

Fizzy makes bubbles large enough to hold herself, Megan, Molly and Danny, and the Baby Sea Ponies carry them to the bottom of the river to search for Pluma's grandfather. Meanwhile, Squirk sends his henchman, a lobster named Krang, to fetch Pluma's piece of the Flashstone. As Pluma makes to hand it over, Spike signals a hidden Buttons, who uses her magic to fling it far out of reach. Impatient, Squirk himself emerges, retrieving the Flashstone piece and imprisoning Spike, Pluma and Buttons in a giant clam shell. He returns to his lair just as Megan's party have freed Pluma's grandfather, and captures them as well.

The children, Little Ponies and Pannas are tied up inside an enormous skull. The roof of the skull's mouth is held up by seaweed ropes, which several turtles are chewing through. Squirk meanwhile goes on a rampage, blasting everything in sight with the Flashstone piece until he reaches the other half in the depths of the river. When he finally has the entire Flashstone, he uses its power to make the water rise, and Dream Valley begins to flood.

Buttons uses her magic to draw a clamshell in between the skull's teeth, just as the ropes give out. Pluma and her grandfather transform together to form a spinning blade, cutting everyone loose. Fizzy once again summons bubbles to let everyone escape. They see that much of Dream Valley is already underwater - but Danny has a plan to stop it. He has the Pegasus Ponies take one of Pluma's nets and circle the sky above him.

As Squirk rises to the water's surface, the Unicorns flatter him, saying they'd like him to be their leader. When his guard is down, the Pegasi drop their net. As Squirk struggles to free himself, Buttons uses her magic to throw the Flashstone into Megan's hand. Megan wishes the water away, taking Squirk and Krang with it. After undoing the damage to Dream Valley, Megan makes one final wish to restore the Paradise Estate - then drops the Flashstone from a great height, shattering it to pieces so it may never be used for evil again.

Squirk and Krang were last seen sucked into an underwater cave, while still trapped inside the pegasi's net, and presumably remain trapped there forever, or else were sucked into oblivion along with the extra water.

Trivia

 * Squirk is one of the most evil G1 villains, alongside Tirek, Hydia, Grogar, and Lavan.