Haunt (When this spell card is put into a graveyard after resolving, exile it haunting target creature.) When the creature this card haunts dies, target player discards a card
Vigilance allows her to continue to defend after attacking, and her abilities provide card generation as well as do damage whenever the player casts a non-creature spell with a mana cost of three or higher
Fill in the gaps that you have in your deck by following the BREAD convention listed above
It does a lot of things but so rarely that it is worth little to the card as a whole
The from exile cast is really pretty powerful, since impulse draw, Conspiracy Theorist, adventures, and many more spells are causing you to exile then cast (or play) and getting more triggers when you do that is a fun archetype, one which I've been hunting for a solid Grixis commander for for a while (there isn't really one yet)
Thoughts on Cavalry Charge: I think this deck out of the box is going to perform fine