If the target creature is an illegal target when Vengeful Possession tries to resolve, it won't resolve and none of its effects will happen. You won't have the option to discard a card in order to draw a card.
20-09-2024
wotc
Gaining control of a creature doesn't cause you to gain control of any Auras or Equipment attached to it.
20-09-2024
wotc
Vengeful Possession can target any creature, even one that's untapped or one you already control.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.