Whenever Herald of War attacks, put a +1/+1 counter on it.
Angel spells and Human spells you cast costless to cast for each +1/+1 counter on Herald of War.
5/1/2012 The +1/+1 counter is put on Herald of War before blockers are declared and combat damage is dealt.
5/1/2012 The cost reduction is based on the total number of +1/+1 counters on Herald of War, not just the ones put on it by its own ability.
5/1/2012 If there are additional costs to cast a creature spell, such as a kicker cost, apply those increases before applying cost reductions.
5/1/2012 A creature spell that’s both an Angel and a Human will cost less to cast for each +1/+1 counter on Herald of War.