Something new for you all :)
This isn't an Alp-Luachra, but a variant that has evolved to live in the salt-filled oceans. I call them Alp-Aigéan. That name probably makes no sense to anyone versed in biology, but whatever.
They are far larger than Alps, with the largest coming to five feet in length, while Alp-Luachra usually have a maximum of one and a half feet. Like Alps, Aigéan are parasitic, and will enter the bowels of large sea creatures to eat what their hosts eat.
Aside from their size, something that makes them far more dangerous to land mammals is their big appetite. When inside a pony, for example, Aigéan will end up eating everything that enters its host's system. When entering a host, some will venture past the cramped stomach and into the start of the intestinal tract. Removal often requires surgery.
These are just some of the reasons why the Aigéan is an extremely dangerous creature, but there's more. Unlike Alp-Luachra, Alp-Aigéan are barely sentient and cannot be reasoned or bargained with. They do not build little societies and they never travel in groups.