I like Orzhov, I like Boros, I like Rakdos, I wanted to put them together, help is greatly appreciated.

The general idea is pretty straightforward, drop low CMC humans and bum rush them until a well timed Falkenrath Aristocrat can come out and clean house.

Champion of the Parish and Ash Zealot really make up the early pressure, with a Blood artist they can keep it coming too making sure you come out at least a little on top when you're playing smart.

Champion of the Parish, into Increasing Devotion followed by an Aristocrat with a Blood Artist out is really quite an absurd amount of power on the field.

Azorius Arrester is meant almost solely as a means of keeping the pace of the game in your favor, throw him out, detain someone, just keep tapping him until they block and you can pull off something with a morbid Tragic Slip or Brimstone Volley. Hellhole Flailer falls into basically the same category but with more offensive power.

The Knights do well to keep the board in your favor early on, I'm thinking they'll mostly play defense and have an Ash Zealot or a Champion of the Parish do the dirty work.