Transmuter Snail

The Transmuter Snail (also called Transmuting Snail or Transformer Snail) is one of the spellcasting vermin of the Kalash continent.
  The Transmuter Snail is, at first glance, just like any other ordinary snail. Unremarkable. You can see the difference in the quick moment where the snail changes shape. If put in a situation where its usual slow pace becomes a hindrance, the small animal will wave its eye-tentacle in specific patterns and "get" new body parts: legs for jumping, fins for swimming, a prehensile tail to reach further. These transformations last for the strictly necessary time: the swim form will be assumed just the seconds needed to cross a puddle, for example.
  The Transmuter Snail can transform its shell, for example, in a defensive form, similar to the spiked murex shell, when caught or when bearing eggs; or a colorful elongated shape to attract mates.
  Every region has its favorite recipe and there are a lot of opinions about the form of the snail that tastes best. In Tu'mir, they prefer them swimming, so they boil them slowly in broth. In the Korana, they like them tailed, so they hang alcohol soaked raisin in the pot: the snails will grow the long tail to catch them and eat them, this way they get drunk and stuck in that shape (and then they are quickly fried). In Almoroc, they like them jumping, so they cook them in tall pots: the hot "floor" makes them grow legs to try to escape. The snails, dead for the heat and the exhaustion, are then chopped and made in sauces to put on bread. Every family has its version of the "snail ragout".
  The differences in the taste of the various snails' forms are minimal, almost inexistent, but every region has a strong feeling about it and there are always two people with different opinions that must discuss this topic.
  Source: https://www.reddit.com/r/worldbuilding/comments/ppikhw/codex_inversus_the_transmuter_snail/