A good suggestion would be to utilise the low-mana cards of the Death splinter. The Skeleton Assassin is probably the best assassin card in the game with his poison (level 6+) and high damage, for just 3 mana! Then there's the Undead Priest & Haunted Spider for just 2 mana each! Pair that with Zintar Mortalis and you have a nice start, leaving 15 mana left for other cards! (Assuming a 25-mana tourney).

I'm running a SteemMonsters Contest right now. You can win a rare gold card or an epic/legendary if you particiapte. Check it out here if you want: https://steemit.com/steemmonsters/@pizzachain/steemmonsters-poetry-contest-steemmonsters-cards-steemmonsters-packs-and-sbi-shares