Malfegor
Legendary Creature — Demon Dragon
Flying
When Malfegor enters, discard your hand. Each opponent sacrifices a creature of their choice for each card discarded this way.
A demon cannot be trusted, and a dragon will not be ruled.
Karl Kopinski
Conflux Promos (PCON)
• #117★Rulings
After you discard your hand and the number of creatures each opponent must sacrifice has been determined, each opponent in turn order, starting with the player whose turn it is if that player is your opponent, chooses which creatures they will sacrifice, then all the chosen creatures are all sacrificed at the same time.
(wotc • 2017-11-17)
Malfegor’s ability is not optional. You must discard your entire hand no matter how many creatures your opponents control.
(wotc • 2017-11-17)
Rulings
After you discard your hand and the number of creatures each opponent must sacrifice has been determined, each opponent in turn order, starting with the player whose turn it is if that player is your opponent, chooses which creatures they will sacrifice, then all the chosen creatures are all sacrificed at the same time.
(wotc • 2017-11-17)
Malfegor’s ability is not optional. You must discard your entire hand no matter how many creatures your opponents control.
(wotc • 2017-11-17)