The Human hero has already been unveiled as the Blood Mage. All three new units are related to the Blood Elves. The new abilities/spells for the Blood Mage are:

Flame Strike: Designed with a five-second delay this spell has a devastating area of effect. The spell, however, can be disrupted if the caster is killed within the five-second window. Few lower levels units within the area of the flame strike will survive.
 

Banish: This spell turns a target ethereal. The target cannot be harmed by physical attacks and cannot attack except with spells. The spell lasts anywhere from 10- 30 seconds, depending on the level of the Blood Mage. Pardo said this spell can be cast on enemy or friendly units and can come in handy on a friendly hero that is wounded and trying to escape.
 

Mark of Fire: This spell transforms any friendly unit into a Phoenix. The Phoenix has increase fire attack capabilities and can do splash damage. However, after about a three-minute duration, the spell ends and the transformed unit dies in a pile of ashes.