Hearthpwn

"BY THE POWER OF RAGNAROS"

"BY THE POWER OF RAGNAROS" is the voiceline from Emperor Thaurissan
so your cards in hand will be reduced by 1 mana at the end of your turn.

Tip 1. Mana reduction mostly encourages OTK (One-turn-kill) decks.
Drawing cards allow more reduction on cards.

Tip 2. The game usually ends around turn 5.
a) When you construct your deck, cards with 5 or more mana cost are not recommended.  
b) Also mulligan for your key combo cards for your starting hand.
c) The most important rule of this brawl is that "Always calculate how much damages you have in hand."
If you miss one turn, your opponent can complete OTK faster than you do.
d) Loatheb can delay spell combo deck as a tech choice.

Tip 3. Cards to counter secret. (Tech card)
Since this is a wild brawl, Mage has the infamous card Ice Block to buy a extra turn to complete OTK.
In order to counter that, Eater of Secrets, Kezan Mystic, Chief Inspector, Flare are really good cards against that.
I personally like to keep Eater of Secrets in opening hand against mage.

Tip 4. Cards to ruin combo. (Tech card)
You can run Dirty Rat and single removal cards to ruin their combo.
Explosive Runes, Potion of Polymorph and Snipe can possibly ruin single-minion based combo deck.

First deck I used is spell OTK hunter
AAEBAR8EtAOuBsUIhbgCDagCtQPtBoAHlwjbCdQR0RTpqwLd0gLf0gLg9QKiigMA
Since I want to pull Malygos with Barnes, I didn't put any other minion. 
Animal Companion, Flanking Strike,  Unleash the Hounds are used to stall the game until I draw all the spell damage cards

Barnes Malygos OTK Spell Hunter Deck by MagicKnight - Mar 15, 2019 View Deck String Export to BBCode Export to Cockatrice Export to MarkDown Export to Html Clone this deck
Minion (2) 1x Barnes 1x Malygos	Ability (27) 2x Arcane Shot 2x Flare 2x Tracking 2x Wandering Monster 2x Unleash the Hounds 2x Animal Companion 2x Baited Arrow 2x Bear Trap 2x Bomb Toss 1x Deadly Shot 2x Flanking Strike 2x On the Hunt 2x Quick Shot 2x Kill Command	Playable Hero (1) 1x Zul'jin
Loading Collection

Second deck I used is spell OTK Mage
Flamewaker and Cosmic Anomaly as main power engine to drive the OTK. 

Spell OTK Mage Exodia Mage Deck by MagicKnight - Mar 17, 2019 View Deck String Export to BBCode Export to Cockatrice Export to MarkDown Export to Html Clone this deck
Minion (11) 1x Archmage Antonidas 1x Babbling Book 1x Eater of Secrets 2x Flamewaker 2x Sorcerer's Apprentice 2x Arcanologist 2x Cosmic Anomaly	Ability (19) 2x Cabalist's Tome 2x Primordial Glyph 2x Cinderstorm 2x Explosive Runes 1x Molten Reflection 2x Arcane Intellect 2x Fireball 2x Forgotten Torch 2x Arcane Missiles 2x Frostbolt
Loading Collection

To counter OTK, C'Thun with lots of armor from warrior class seems good to out-value the spell power in opponent hands

If you have any other tips, or improvements, comment below. We strike to make a better game experience.