Ruthless Deathfang
Creature — Dragon
Flying
Whenever you sacrifice a creature, target opponent sacrifices a creature of their choice.
"Bring forth the dead, their skull-grins and rattle-bones. We will feast upon their wailing ghosts." —Silumgar, translated from Draconic
Filip Burburan
Dragons of Tarkir (DTK)
• #229Rulings
Notably, the “legend rule” does not cause any permanents to be sacrificed. They are simply put into their owners' graveyards.
(wotc • 2015-02-25)
Ruthless Deathfang's triggered ability will trigger whenever you sacrifice any creature, including Ruthless Deathfang itself. It will trigger whenever you sacrifice a creature for any reason, including to pay a cost or as the result of a spell or ability (such as an opposing Ruthless Deathfang's ability).
(wotc • 2015-02-25)
Rulings
Notably, the “legend rule” does not cause any permanents to be sacrificed. They are simply put into their owners' graveyards.
(wotc • 2015-02-25)
Ruthless Deathfang's triggered ability will trigger whenever you sacrifice any creature, including Ruthless Deathfang itself. It will trigger whenever you sacrifice a creature for any reason, including to pay a cost or as the result of a spell or ability (such as an opposing Ruthless Deathfang's ability).
(wotc • 2015-02-25)