The ikuchi constantly emits a thick, nonflammable, yellowish oil. When the ikuchi is underwater, this oil makes the water within 30 feet of the ikuchi difficult terrain. Each time a creature moves more than 10 feet through this area it must succeed on a DC 15 Strength saving throw or be restrained by the thick oil until the end of its next turn. A creature under the effects of a freedom of movement spell or similar magic is immune to the effects of Ikuchi Oil.