Some spells cost the practitioner that casts them their very lives, either through exertion or miscalculation. The creature does not know to which type its summoning belongs but suspects the latter.
It appeared in the chamber, claws scraping stone and wings brushing the cramped ceiling, and watched the summoner collapse before it. It wondered, for the first time, what it should do.
It waited for a command, but none came. It eventually became hungry and ate.
It still waits, wandering the halls of the mage’s now abandoned tower, looking for someone who can provide it purpose or perhaps another meal.