The Crown of Acorns is the ancestral crown of the House of Acorn, and possesses certain abilities.
Presumably, it increases the power of the wearer and its power is in turn increased by the Sword of Acorns. The Crown is also capable of counteracting the crystallization effects of the Zone of Silence, allowing King Acorn to escape death due to the transformation. Merlin Prower revealed that the Crown apparently also had abilities that would save the failing Ancient Walkers and maintain the curse of imprisonment on Mammoth Mogul's Emerald. It was worn by the King for much of the series before being stolen and corrupted by Mammoth Mogul with the aid of his minions, the Destructix only to be destroyed shortly afterwards by Sir Connery.