Make sure you have a balanced deck with many cards. Especially low mana cost ones. Have it centered around your faction.
Stay at your one portal for most of the game. Only jump into the right patch when there are only two weak enemies left, but make sure you return everything to your portal after that, because Helena will spawn stronger enemies the very next turn. There will only be 2 or 3 occurrences when you will be overwhelmed with 14 or so enemies in a battle. Have
bulky row 1 cards to withstand damage. And constantly heal them with
Gwidyon and the Kingdom Spells if you can. Heal a lot for it's a defensive mission. You can get a lot if you spawn every turn, because Helena sometimes throws 1-3 enemies at a time which will be decimated even if there rare or legendaries. If you play this right, you can get even over 30 cards against Helena at the end of the mission.
If you're playing Kingdom, put as many
Terror Blades and
Armored Longbowmen as you can.
Light Infantry too, but they'll probably die eventually 'cause they're in row 1 without much health. Their
veteran abilities will increase their damage and accuracy after every battle, and there are a lot of battles in this mission. I've had Armored Longbowmen have 160+ base damage at the end of mission 9, because there are so many battles.
If you're playing Dragon, or even if you're not, this is a good strategy:
Mountain Wyrms are worth it in all factions because of it's 40 AoE.
Dragoneye Sorcerer does 20 AoE, and with
Breath of the Ancients, you'll slaughter everything because the two aforementioned cards can use their special every turn. So make sure you cram those cards.
Mana Convergence is good 'cause the computer usually has 6+ mana wells. If your luckier with rates, use
Krylyr and
Rage Dragon for their AoE.
I haven't gotten to mission 9 with Demons Missions yet. Volcano Fiends and Filth Elementals dish out some AoE. Screaming Boulders are good row 1 bulks.
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