Introduction
Supratika is an elephant, the subject, together with the tortoise Vibhavasu, of a curse that bound the two, once brothers in an earlier life, to fight each other eternally in the form of an elephant and a tortoise, until both were finally eaten together by Garuda.
The curse
According to the story told in the Mahabharata's Adi Parva, Supratika and Vibhavasu had been sage brothers in an earlier existence, whose mutual contempt and quarrelling led a sage to curse them to be reborn as an elephant and a tortoise of enormous size, doomed to fight each other without end in a great lake.
Death by Garuda
Garuda, seeking a suitable meal, came upon the two locked in combat, seized both at once, one in each set of claws, and ate them in a single act, which is cited in the epic as an illustration of Garuda's tremendous size and strength.
Meaning
The story is generally told as a demonstration of Garuda's power rather than as an independent moral tale about Supratika himself, though the underlying curse narrative, of quarrelsome sages reborn as eternally warring animals, is sometimes read as a caution against enmity.