Lobstrosities are bizarre creatures that live on the beaches of the Western Sea. They look like a cross between scorpions and giant lobsters measuring about four feet long, with sharp serrated beaks, and eyes on stalks.
Roland Deschain observes that they constantly murmur questions: Dad-a-chum? Dum-a-chum? Ded-a-chek? Did-a-chick? Later discovering they are venomous but despite this they are edible which is proven by Eddie.
They assume what Roland calls "The Honor Stance" when the waves of the ocean come in. "The Honor Stance" is when they hold their claws up in the air. This stance is held until the waves wash over them. The lobstrosities also appear to be more vicious at night.
One of these creatures is responsible for taking two of Roland's fingers, one of his toes and a chunk from his calf. Eddie also has a dream he is ripped apart by these creatures while tied up on the beach by Detta. Jack Andolini met his end by these creatures after his hand was blown apart by his gun.
It is thought that the Lobstrocities are perhaps the same creature as one on a different level of the Tower in Bridgton, Maine. Here a Thinny is accidently created by the US military who are doing experiments under "Project Arrowhead" and rips a hole in Todash Space releasing hordes of Todash monsters on the unsuspecting inhabitants of the town. One of the creatures that kills a townsperson, Ollie, bears a striking resemblance to the Lobstrositites.