Mulligan heavy for Gadgetzan Auctioneer (throw away all other cards except Arena Treasure Chest) - it is most important card for finding your combo quickly.
You can also leave Prophet Velen in starting hand to not risk that he will be at bottom of deck.
/ 10.03.2019 Updated for Brawliseum
What this deck tries to do is to play Prophet Velen, Malygos or both (but Velen is a lot better), then spawn additional copies of them with Faceless Manipulator and Mirage Caller and play Mind Blast to kill opponent. I decided to cut Holy Smite becasue I always finished my opponent with Mind Blast and Holy smite were used only to ping single minion + cycle. Instead I went with more healing (Binding Heal).
Use Gadgetzan Auctioneer and cheap spells, as well as Arena Treasure Chest to cycle through your deck. The combo is pretty easy to assemble, it is lilkely to make as early as turn 5, but you have to mulligan heavy for Gadgetzan Auctioneer.
Spirit Lash helps you to kill all enemy 1/1 minions and survive until you play combo. You can sometimes use it with Malygos if enemy buffed their minions (it will also probably heal you back to 30) and still have win condition with Prophet Velen.
Unfortunately this deck is 50-50 versus Rogue whcih is about 70% of all decks in this brawl (lost all games to Spirit of the Shark + some shenenigans) , so dont expect high results. Try this deck if you want to play something different and have some fun.
You can sub Geddon for Mossy Horror