Kelpie

A water-spirit that wears the shape of a stray horse grazing by a lonely loch, its mane always damp. Touch it and you cannot let go; it bolts for deep water and holds you under until you drown, then feeds. Kelpies haunt fords and millponds, and a riderless horse near dark water is rarely a kindness.

Hooves: bludgeoning, melee 5 ft, +2 to hit, 1d8+3 bludgeoning. Drowning Lure: control, a creature that mounts or touches the kelpie's horse form is stuck fast (save Dex Quick to avoid) and dragged into deep water, taking 2d6 drowning damage each round until it breaks free, cooldown 3 rounds.

Shapechanger: appears as a docile horse or pony, its mane always wet. Amphibious: breathes air and water and swims at speed. Senses: Night Vision (60 ft), Living Sense (feels the living, 60 ft).