Sword of Light and Shadow
Artifact — Equipment
Equipped creature gets +2/+2 and has protection from white and from black.
Whenever equipped creature deals combat damage to a player, you gain 3 life and you may return up to one target creature card from your graveyard to your hand.
Equip 
Illustrated by
Assassin's Creed#262MythicEnglishLegality
Rulings
Jun 7, 2013
You may put the triggered ability with no targets. However, If you choose a target creature in your graveyard, and that card is an illegal target when the ability tries to resolve, it won’t resolve and none of its effects will happen. You won’t gain 3 life.