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 
Bruce Brenneise
Assassin's Creed (ACR)
• #125Rulings
If you choose a target creature card in your graveyard and that card is an illegal target by the time the triggered ability tries to resolve, the ability won't resolve. You won't gain 3 life. If you don't choose a target at all, you just gain 3 life.
(wotc • 2020-08-07)
The triggered ability can target a creature card that was put into your graveyard as a result of state-based actions immediately after the combat damage that caused the ability to trigger.
(wotc • 2020-08-07)
Rulings
If you choose a target creature card in your graveyard and that card is an illegal target by the time the triggered ability tries to resolve, the ability won't resolve. You won't gain 3 life. If you don't choose a target at all, you just gain 3 life.
(wotc • 2020-08-07)
The triggered ability can target a creature card that was put into your graveyard as a result of state-based actions immediately after the combat damage that caused the ability to trigger.
(wotc • 2020-08-07)