Looking back at another Champ 1 run last season where I ranked as high as 13 briefly with 2 days left before i got dragged down to earth to rank 95 (OUCH)...these are the cards that beat me that I need and that YOU should need at the Champ level.
#5 Spark Pixies - Must have in the Yodin mirror (I finally got one on rental but it was the only one available)
At champ 1 Yodin is everywhere..if you don't have Yodin you simply cannot win...you can try Lir Deepswimmer yes, but it doesn't overpower Yodin if they're using melee opportunity or sneak guys. The one card that is required at least for me is Spark Pixies. This guy is simply unstoppable when the Monkey and Flame Imp come in to boost speed. With those two cards Spark Pixies is NINE speed, and has flying AND dodge. With Yodin he has BLAST and STUN. At FOUR freaking mana. In the mirror he's a must include and if you don't have him you lose.
#4 Naga Warrior - must have in low mana matches
At 5 mana this thing bloats to insane melee and speed levels and cannot be stopped. It'll beat the living crap out of you and you lose if you can't kill it. It's Alpha and Beta so it should be easy to rent.
#3 Dark Ha'on - Taunt with huge body, reflect, void and more goodies
This guy along with Robo Dragon Knight is pure nastiness. Flying..scavenge..taunt..void..magic reflect. When you're playing water or a lot of magic the game ends right away. You can't kill it...at ALL..and when you finally do it you've already put yourself in a losing position. The taunt is the worst since you have to kill it first before attacking anyone else.
#2 Mimosa - -1 Range, Void and Afflict. If you're playing a water and healing strategy it's pretty much game over. ALL their monsters get VOID and AFFLICT. No healing, no magic.. On top of that your range guys get a downgrade..that's what Magic players call a HOSER. Water was really popular next to Fire at Champ 1 so Mimosa is a must have.
#1 Robo Dragon Knight - the mother of all middle finger cards
This card is so nasty that it's unrentable..yes you can buy it on the market for a cheap $2 but it's cheap because it's a reward card..if it was in Untamed or Beta is a $25 card. It stops magic with void and magic reflect, return fire to stop range, divine shield to stall and piercing as cherry on top. It has a HUGE armor ass and a HUGE health ass so you'll be spending the entire battle trying to kill it before it by itself kills you. A melee strategy is good with opportunity,sneak or snipe against it, but when it's at tank position and you have no sneakies it'll mess with you in the worst way.