Rat
A rat is no rival for a nest, but a roaming predator of immense strength.
Rats enter the world from beyond the map. They roam for a time, scent slimes from a great distance, and pause to fix on prey before a swift lunge. Water does not stop them.
A danger with a rhythm
A sleeping rat is no assurance of safety. Each visit has its own waking, hunting and departure phases. Watching that rhythm explains why the same ground may seem safe for a time, then be avoided again.
Meeting a colony
The rat hunts slimes of every species and devours its kills entirely instead of leaving a carcass. Its great health and powerful bite can wound even a led group. If defeated, it stays away for a longer interval; later, another visit may begin at the map edge.
The rat slept through the rain. No forager dared pass it, though it lay still for a long time.
