The Temmies are a horde of ravening, senseless demons, completely blind from the pressing dark and roiling in a massive wave through the fetid waters and mud banks of the Dead Swamp. Any prey they find is rolled over and consumed as though by a swarm of piranha, not even stopping as they writhe further into the muck and grime. The fact they once were cute makes them more horrifying.
Bob lives among his Temmie brethren, the most intelligent of the screaming, slavering beasts. He seems to direct them in their pillaging.