A demon cannot be trusted, and a dragon will not be ruled.

Malfegor

Flying
When Malfegor enters, discard your hand. Each opponent sacrifices a creature of their choice for each card discarded this way.

Iconic Masters

Flying
When Malfegor enters the battlefield, discard your hand. Each opponent sacrifices a creature for each card discarded this way.

Commander Anthology

Commander 2011

Magic Online Promos

Conflux

Flying
When Malfegor comes into play, discard your hand. Each opponent sacrifices a creature for each card discarded this way.

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.

Malfegor’s ability is not optional. You must discard your entire hand no matter how many creatures your opponents control.