Deadly Riposte deals 3 damage to target tapped creature and you gain 2 life.
"Automatons are fast, precise, and tireless, but they all share one weakness: predictability. Learn their patterns. Strike when they're vulnerable."
—Horance, Urzan general
If the target creature is an illegal target as Deadly Riposte tries to resolve, it won't resolve and none of its effects will happen. You won't gain life.
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.