Last week I played Mono-White Devotion and this week I've been working on Mono-Blue Devotion. I think I finally got to a build that I'm happy with. It primarily revolves around Grand Architect. The Architect provides enough devotion to get a pair of extra Elemental tokens off Master of Waves. Then the Architect allows you to tap itself, the Master, and all the Elemental tokens for mana (two per creature) to power out a huge Walking Ballista on the same turn! Besides this powerful combination, the deck has Trinket Mage to find more Walking Ballista and for the toolbox sideboard. It also has land hate in the form of Spreading Seas and Field of Ruin as well as countermagic (Spellstutter Sprite and Mausoleum Wanderer) that adds to our devotion for the Master. To top it all off, we have Academy Ruins to keep rebuying Walking Ballistas.
+1 Chalice of the Void (primary target early)
+1 Trinket Mage
+1 Engineered Explosives (The Rack and Shrieking Affliction)
+1 Pithing Needle (Liliana of the Veil or Mutavault)
+1 Basilisk Collar (just to gain life)
Four-Color Death's Shadow
Overall, I recommend giving this deck a shot. It does some powerful things and has a lot of interactive cards to disrupt the opponent as well as some powerful sideboard options, including a Trinket Mage toolbox.