Hi, I don't know much about the LotFP game, but saw the 'weird monster competition' and threw my hat into the ring. Probably asking for a fall, but tried to meet the brief anyway!
Here is my failed beast - the idea was for the monster to be part of the back drop to an adventure - why are seaside villages being found empty ...
'Man-fisher'
#stats {similar to a whale or giant squid, but is of higher intelligence}
This sinister creature lives in the deep seas, but when prompted by hunger comes in to feed at the sea shore.
When in this feeding mode it deploys a 'prey organ' in the white water of the waves that lap at the seashore.
The 'prey organ' is made up of a mass of translucent barbed tubes that it roils in the white water, and these are virtually undetectable until it is too late.
A victim entering the white water will be ensnared by the 'prey organ' which it wraps around the legs and torso of the victim like tight corse rope. If the victim is strong it will also pin down it's arms.
The Man-fisher will not usually (immediately) drown the first victim it catches, but rather it will use that first victim as 'live bait', allowing the victim to bob and thrash at the surface crying out for help, before pulling them under the surface again. As the victim tires it might even aid the victim staying afloat.
The commotion of the 'bait-victim' usually draws further victims into the water (unwittingly trying to save what they believe is a drowning person).
It usually only keeps one victims alive at a time as 'live bait', the rest of the victims are usually immediately drowned and passed to a bloated whale-sized feeding organ located in much deeper water.
It's favourite kind of 'live bait' is a child, which it has learnt over the centuries yields a large number of follow-on victims. Whole seaside villages have been reduced to ghost towns by the Man-fisher.
The 'prey organ' can also capsize small fishing boats if the creature desires, or it is threatened.
The barbed tubes are more designed for gripping, and so usually do little physical damage. The primary attack of the Man-fisher is drowning. To break its grip requires a great feat of strength.
Once the 'feeding organ' is full, the creature usually returns to the deep seas to digest its victims, which depending on the number of victims caught will sait its appetite for months or even years.
The Man-fisher is nearly impossible to kill. It has hundreds or barbed tubes as part of it 'prey organ', which are very hard to see it the whitewater and so to cut or spear them in the break water is incredibly difficult. If damaged or cut, they repair or grow back, which has led some scholars to call the creature the Sea-troll, but it is probably more closely related to a multicellular creature (albeit massive and intelligent).
The bloated 'feeding organ', looks like a giant translucent sack, and is usually located some 60 to 100 feet from the 'prey organ'. It is usually in deep water, and so unless the water is exceptionally clear, it is difficult to see from the surface, and hence very difficult to target. If the 'feeding organ' is genuinely threatened, the creature will withdraw back to the deep sea to recover, before returning and selecting a new location to 'fish'.
While the creature is quite capable of capturing sea creatures for food, it prefers targeting small seaside settlements which yields easy prey. Very few people even know of the existence of this creature as it leaves very few witnesses behind.
It is vulnerable to electrical attacks, which usually cause it to flee, but will clearly also harm anyone else in the water, including ensnared victims.