Bawkatrice, Basigator and Burdusa

One can only get a Bawkatrice by having a Beckaw (upcoming Pokemon) lay an egg which will then be "incubated by" (more like attached to) an Ekans or Poliwhirl, and to have only 5 Pokemon carried with you. After some time, the egg will hatch into a Bawkatrice rather than a Chuck or baby Beckaw. Bawkatrice have a peculiar weakness to Linoons and Roosterades. The trio is a fire/poison type

Basigator: It swims through mud and quick sand waiting for prey to pass by. Its breath can damage the respiratory system of those who smell it.

Burdusa: Less armored than its pre-evolved form but more powerful, eye contact with it freezes an opponent, leaving them vulnerable.