2006-05-01 : If a source you control would deal damage to multiple creatures and/or players simultaneously, all of that damage is doubled.

2006-05-01 : If damage that would be dealt to a player or creature is affected by both Anthem of Rakdos and a damage prevention effect, that player or that creature’s controller chooses the order to apply the effects. In most cases that player will want to prevent damage, then double what’s left.

2006-05-01 : The first ability triggers once for each creature you attack with. If you attack with three creatures, for example, they’ll each get +2/+0 and you’ll be dealt 3 damage.

2006-05-01 : The hellbent ability doubles the damage dealt to you by Anthem of Rakdos itself.