I have a few play ideas in my head, but only one written down.
Hand:
Akroan Crusader x 2
Vanguard of Brimaz x 1
Mystic Monastery x 2
Island x 1
Plains x 1
Draw:
Turn 1: Phalanx Leader
Turn 2: Howl of the Horde
Turn 3: Battlefield Thaumaturge
Turn 4: Icy Blast
Turn 5: Crowd's Favor
Turn 1:
Play Mystic Monastery, tapped. Draw Phalanx Leader.
Turn 2:
Untap all Lands. Draw Howl of the Horde. Play second Mystic Monastery, tapped. Tap first Mystic Monastery for 1 Red Mana to cast the first Akroan Cruader.
Turn 3:
Untap all Lands. Draw Battlefield Thaumagturge. Play Plains. Tap first Mystic Monastery for 1 Red Mana to play second Akroan Crusader. Tap second Mystic Monastery and Plains for 2 White Mana, cast Vanguard of Brimaz.
Turn 4:
Untap all Lands. Play Island. Draw Icy Blast. Tap Island and Plains to pay for the costs to cast Battlefield Thaumaturge. Tap Both Mystic Monasteries for 2 White Mana, cast Phalanx Leader.
Turn 5:
Untap all Lands. Tap Mystic Monastery for 1 Red Mana, tap second Mystic Monastery for any color, tap Plains for 1 White Mana to cast Howl of the Horde.
Declare ALL creatures to attack.
Tap Island, cast Icy Blast.
What happens here is that the declaration of the attack meets the stipulation of Howl of the Horde that allows you to cast it two more times in addition to the initial cast, meaning it casts Icy Blast three times.
So what, you cast that three times, but what about X costs?
That's where Battlefield Thaumaturge shines, his effect reduces any additional target cost of an instant or sorcery, beyond the first, by 1 Colorless mana.
The X cost for each target IS exactly the cost of 1 Colorless Mana.
This combination of X cost plus Battlfield Thaumaturge results in the ability to target an infinite number of creatures for only the initial cast cost, all other X costs are negated. And the same stands for each copies of the Icy Blast, both of them.
Now how you choose your targets matters 100% percent.
Tap Battlefield Thaumaturge first (yes, I know he's already tapped from the declared attack. Doesn't matter, this is just to make it the target of the spell to trigger their Heroic Effects) making him Hexproof for the rest of the turn. Tap both of your Akroan Crusaders second put two 1/1 Red Soldier Creatures with Haste onto the Battlefield. Target Vanguard of Brimaz next. Place a 1/1 White Cat Soldier with Vigilance onto the battlefield. Tap Phalanx Leader last. This allows his Heroic effect to put a +1/+1 counter on each creature on the battlefield, including all the newly created tokens.
And this, people, is only the FIRST cast of Icy Blast, there are still TWO more copies to be cast.
And that you will, repeating the above cycle two more times. However, on the last cast of Icy Blast, after you target your creatures, you will also target your opponents creatures, all of them for no cost, to remove all defenders. Because of Phalanx Leader's Heroic, Vanguard of Brimaz is a 5/5 by the last cast, triggering the Ferocious effect, making it so ALL of the creatures tapped, ( including yours), cannot untap during their next Untap Phase (effectively, everyone skips a turn, whoop-dee-doo, epitome of neglible as you will have 6 Red Soldier Tokens and 3 White Cat Soldier Tokens left untapped, high-powered and ready to defend).
Now tap a token to pay for the costs to cast Crowd's Favor, which will allow you to target Phalanx Leader again, activating his Heroic Trigger yet again, leaving up to a total of 4 +1/+1 counters on all your creatures.
The end result on the battlefield will boggle your mind:
Akroan Crusader x 2, both 5/5 and attacking.
Vanguard of Brimaz x 1, 6/6 and attacking.
Battlefield Thaumaturge x 1, 6/5 and attacking.
Phalanx Leader x 1, 6/5 First Strike, attacking.
Red Solider Tokens x 6, 2 x 5/5, 2x 4/4, 2 x 3/3, one 3/3 tapped, rest untapped.
White Cat Soldier Tokens with Vigilance x 3, 1 x 5/5, 1 x 4/4, 1 x 3/3, untapped.
-All Attackers Unblocked, for a total of 28 Damage to (a) hapless target(s).
-That's 14 Creatures on the field by turn 5, lowest 3/3.
-On your next attack phase, you could attack for 64 the next time you attack with all, or attack with some and keep some up for defense.
- All with only 4 Lands.
Whichever way you lay it out, you most likely have killed your opponent.
If it's a multiplayer game, you'd have killed at least one opponent and are leaving the others shuddering and scrambling to conspire together to remove you from the game.