Ice Magic

Ice Powers are the abilities possessed by the Ice King's Crown. Ice King claims to have stolen them, presumably from another wizard, and sealed them in his crown. In the episode "Holly Jolly Secrets Part II," it is revealed that he found the crown in Scandinavia as a collector, unaware that the crown would grant him ice powers or drive him into insanity. Consequently, he loses his Ice Powers if his crown is removed or lost. The main application of Ice King's powers are the large icy lightning bolts he shoots at his opponents. He can also manipulate the water in the air to create shields, and can even create torrents of icy weather at will. As seen in "The Eyes," the Ice King is also able to manipulate any ice in the area by use of telekinesis.

While the Ice King is rather incompetent and weak on his own, the ice he controls is extremely resilient, completely incapacitating anyone frozen within preventing any movement. It's only weakness is the common fragility of ice which can shatter but it still can show strength in such: after freezing Princess Bubblegum (who had mutated into a giant monster courtesy of The Lich) in "Mortal Recoil," the ice prison did shatter but it was strong enough to shatter Bubblegum's entire body in the process. The freezing, which can completely stop all life functions and totally immobilize the target, can be both a blessing and a curse; while it does allow for Ice King to easily disarm opponents, it becomes a burden when he must carry his target while they're still incapacitated, sometimes relying on a cart (in the Ice Kingdom) to bring someone he had frozen to imprison in his castle.

Even though the Ice King does possess a weakness towards heat and fire, he can withstand it for a period of time if need be. When trying to protect Finn and Jake from Scorcher in "Hitman," he created a strong ice dome that withstood the fire elemental's power for a longer period of time than one would typically consider for the interaction between ice and fire.

Another common use of his Ice Powers is the Ice King's ability to fly. This is done through the animation of his beard, which flap as wings. In the episode "Loyalty to the King," it is revealed that if his beard is shaved off, he loses his power to fly.

In "Mystery Dungeon," Ice King's ice powers are greatly weakened in the very hot and humid environment.

Fridjitzu
Fridjitzu is an extension of the Ice King's powers. It is a play on the words "Frigid" and "Ninjitsu." Whereas his main attacks are generally broad and unfocused, the techniques held in the Ice Ninja manual Ninjas of the Ice: The Art of Fridjitzu enable the Ice King to use more refined attacks, and even create weapons out of Ice. He generally keeps this range of his abilities a secret and rarely uses it in battle. Finn and Jake learned a few Fridjitzu techniques in when they found the manual in Ice King's home, but forgot what they had learned shortly afterwards.

Trivia

 * In "What Have You Done?" Ice King attempted to show Princess Bubblegum what he could do with his dandruff, it resulted in giving the Candy People Freezer Burn Flu.
 * Ice King also has an ability called Wizard Eyes that causes him to see bizarre and disturbing things (spirit realm). It is revealed in "Holly Jolly Secrets Part II" that he can't control whether or not he sees the visions, even without the crown.
 * It is shown that Ice King can make large objects with his ice powers, as in "Mortal Folly," where he makes a large ice dome in an attempt to trap Finn and Jake so he could get their permission to marry Princess Bubblegum.
 * The crown he wears could make a person insane, changing a regular human's skin color to blue and lowering their core temperature.
 * The Ice King can see all things in the spirit realm—a side effect of the crown turning him into a wizard, as seen in "Beyond this Earthly Realm."
 * It is revealed that the Ice King can make living things out of snow as seen in the episodes "Prisoners of Love," "Holly Jolly Secrets Part I," "Holly Jolly Secrets Part II," "When Wedding Bells Thaw" and "Still".
 * As confirmed in "I Remember You," the crown kept Simon Petrikov alive through the Mushroom War as he turned into the Ice King. However, he is not completely immortal, as revealed in "Finn the Human."