Fiendlash
Artifact — Equipment
Equipped creature gets +2/+0 and has reach.
Whenever equipped creature is dealt damage, it deals damage equal to its power to target player or planeswalker.
Equip 
A fiery scourge for both flesh and soul.
Antonio José Manzanedo
Rulings
If the equipped creature isn't on the battlefield as the triggered ability resolves but it had lifelink when it left the battlefield, you will gain life.
(wotc • 2021-07-23)
Use the equipped creature's power as the triggered ability resolves to determine how much damage is dealt. If the equipped creature is no longer on the battlefield at that time, use its power as it last existed on the battlefield.
(wotc • 2021-07-23)
Rulings
If the equipped creature isn't on the battlefield as the triggered ability resolves but it had lifelink when it left the battlefield, you will gain life.
(wotc • 2021-07-23)
Use the equipped creature's power as the triggered ability resolves to determine how much damage is dealt. If the equipped creature is no longer on the battlefield at that time, use its power as it last existed on the battlefield.
(wotc • 2021-07-23)