The whole question goes like this:
What magical abilities such animals could develop or magically enhance existing ones to greatly increase the likelihood of drastically outliving an average specimen
- An indeterminately-growing animal is, well, an animal that never stops growing
- The animals I'm mostly interested in are snakes, lizards, amphibians and fish (mainly sharks) as well as crustaceans (if that helps)
- Most animals (the exception are the magical species) in my world start manifesting magical abilities with clearly visible effects after approximately 100 years in areas with mundane magical activity (also varies with size and intelligence, with small and intelligent being the fastest to achieve it)
- Since the abilities develop during life, and are a subject to environment and thus diverge between individual specimens, but still share visible common elements across the whole species (think bending in ATLA)
- The only factor i can think of that my magic system would not support in almost any form of rapid transformation (shapeshifting etc.), otherwise anything goes, demons, ghosts, gods, undead, eldritch horrors and the like
A serpent developed a connection with a dark deity while living near its temple, and now said deity recognizes the serpent as a pet/living weapon, and with it's followers cares for it.
A species of giant swamp toads has a tendency to "learn" how to bend light around itself to camouflage for hunting and create mirages to confuse predators, which can evolve into the ability to affect not only light, but also empty space for short periods, improving hunting and evading abilities.