Shellycoat

Despite being short and squat, this creature’s relationship with a troll is undeniable. The kinship is most notable in the long arms and thick, pebbly hide.
Long Handed and Toad-like. The shellycoat is a warped and spiteful creature also called the Iamh fada, or “long hands,” and they are frequently referred to as bridge trolls. Despite being fey, they are distantly related to true trolls. Unlike those tall, lanky creatures, a shellycoat is dwarfish and toad-like, with short, bent, legs and freakishly long arms with swollen, distended joints. It can further dislocate and stretch these joints to alarming lengths.
Bridges and Pools. The shellycoat can be found in abandoned wells or behind waterfalls, in deep tide pools, or beneath the ice of frozen ponds, but their preferred haunt has always been under bridges. They are most active during nighttime and on heavily overcast days, because of their mortal dread of sunlight.
A shellycoat's favored tactic is to lie in wait under the water or ice (or bridge) and surprise its prey. It strikes outward or upward from its hiding place to snatch children, livestock (preferably goats), and lone travelers or fishermen. Prey is dragged down to the shadows and water to be robbed and devoured.
Shining Garments. A shellycoat will always have fashioned for itself a coat, cloak, or shirt of colored pebbles, glass, and polished river shells. These adornments are crude but beautiful and sometimes magical.