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 and drive him into insanity. He (or whomever uses the crown) cannot use the Ice Powers if the crown is removed from the head or lost.
While the Ice King is rather incompetent and weak on his own, the ice he controls is extremely resilient, and can completely incapacitating anyone by freezing them, preventing any movement. He can create both snow (as seen in "Prisoners of Love") and ice in many forms, living and non-living, such as lightning bolts and snowmen. He can also manipulate the water in the air to create shields, and can even create dangerous torrents of icy weather at will.
Another common use of his Ice Powers is the Ice King's ability to fly. This is done through the movement of his beard, which flaps 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. As seen in "The Eyes," the Ice King is also able to manipulate any ice in the area by use of telekinesis. In "Princess Potluck" it is revealed that Ice King can sense whether something comes to the Ice Kingdom.
Ice King also has Wizard Eyes that allow him to see spirits from the Spirit Realm, normally invisible from the material plane. He first mentions his Wizard Eyes in "Mortal Recoil," and further explains and utilizes this ability in "Beyond this Earthly Realm." It is revealed in "Holly Jolly Secrets Part II" that Ice King apparently can't control whether or not he sees these visions, even without the crown.
The Powers's only weakness is the common fragility of ice, which can shatter, but this attribute actually proves useful on some occasions: after Ice King froze 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 can completely stop all life functions and totally immobilize the target, as seen in "Hitman."
Even though the Ice King does possess a weakness towards heat and fire, he can withstand it for a period of time if necessary. While 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. However, in "Mystery Dungeon," Ice King's ice powers are greatly weakened in the very hot and humid environment.
FridjitzuFridjitzu 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 when they found the manual in Ice King's home, but haven't used them since the episode "The Chamber of Frozen Blades."
- In "What Have You Done?," when Ice King attempted to show Princess Bubblegum what he could do with his dandruff, he ended up giving the Candy People Freezer Burn Flu.
- The crown Ice King wears is capable of turning one insane, changing his regular human's skin color to blue, and lowering his core temperature.
- The Ice King can see all things in the spirit realm—a side effect of the crown turning him into a wizard, and an ability that turns out very helpful to Finn, as seen in "Beyond this Earthly Realm."
- In "The Cooler," Ice King is shown to shoot ice through his feet.