Ice Elemental

'Frost Form. 'The The elemental can freely pass through nonmagical, unworked ice or snow. While doing so, it doesn't disturb the material it moves through and it is unaffected by difficult terrain or movement-impairing effects that would be caused by arctic conditions. If the elemental makes contact with a body of water or liquid that is principally water (not counting water-based creatures), it freezes the liquid to a depth of 6 inches over a 10-foot area around it. This ice lasts for 1 minute. In addition, a creature who touches the elemental, hits it with a melee attack, or is swimming in water frozen by it suffers 3 (1d6) cold damage. If caught swimming, that creature is also pushed to the nearest unoccupied space of swimmable water.

Freezing Aura. Any creature that starts its turn within 10 feet of the elemental takes 3 (1d6) cold damage.

Actions
Multiattack. The Ice Elemental makes 2 slam attacks.

Slam. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 15 (2d8 + 5) piercing damage. The target must succeed on a DC 13 Constitution saving throw or take an additional 10 (3d6) cold damage and has their speed reduced by 10 ft until it takes fire damage or completes a short or long rest.