Sideboard Reasoning:
Gatekeeper of Malakir  - Been looking at maindecking him, as a 2/2 for BB isn't bad, but his kicker is a nice tempo boost usually.
Fiend Hunter - This guy is another Banisher Priest, that helps swing tempo my way, also a guy i've looked at maindecking
Herald of Torment - a 3/3 flyer who can be bestowed? another favorite sideboard option
Elite Inquisitor -  Tribal decks can be popular in my meta, and he's a neat conditional sideboard guy
Lifebane Zombie - I feel like he should almost be maindeck, but he does nothing agaisnt Blue/Black/Red which a lot of people run, so he's a great sideboard option agaisnt G/W
Royal Assassin - In decks with a grinder matchup, he's awesome, but i'd usually rather cast Banisher Priest/etc for the removal of any creature and sometimes waiting for something to tap means he doesn't do much.
Cruel Edict - I like it whenever you run into something annoying like witchstalker - which is becoming popular here.
Zealous Persecution - it can at times be a boardwipe and alpha strike if playing agaisnt a similar aggro deck
Mortify - Sometimes more removal is needed
Preeminent Captain - I don't run many soldiers, but the first strike isn't horrible.
Launch the Fleet - This card is nuts in the deck at times
Grim Haruspex - card draw is nice
Mobilization - Sometimes a token for 3 mana late game isn't the worst use of mana
Hushwing Griff - hate for a few decks