The Biter Pokemon
Ringuana are totally fixated by their own tails, and will waddle around with their tails in their mouths. Don't fight it, or they'll bite back.
The Toroid Pokemon
Torusaur's scaly hide renders it nearly impervious to attack. It hunts by asphyxiating prey trapped in its ring-shaped body.
The Infinity Pokemon
When a Soroboros gets old, its head will detach from its body and become a Ringuana. For this reason, scientists claim it is essentially immortal.