Janna

This makes use of Janna's overpowered Divine Grace spell from to generate immense value and literally blow enemy boards away. With its cost reduction and card draw, it can rapidly go infinite when combined with Janna's other card discounts.

The one downside of Divine Grace is that it reduces your hand size by 1 each time you draw and play it, so stacking up card draw from and Janna's champion spell with negates the downside and ensures you'll draw into your next Divine Grace.

Later in an adventure, this can easily win the game on turn 1, with nearly infinite combo loops, especially if you can find cost reduction on Janna or your spells.

Designed for aggressive tempo, this build allows Janna to be played on the first turn. Since she counts as a 'cost reduced' card, she discounts the top cards of her deck, immediately starting the cost reduction and draw engine.

This sets up Janna's value loop with Echoing and Searing while using Chosen to close out games. Echoing 'cost reduce's her champion spell while Searing Brilliance does the same to another spell. Then, Augment turns each card play into permanent stats for Janna while Overwhelm helps close out the game.

This is one maximally accessible way to complete the 5* Diamond Vault quest with Janna by beating Lissandra.

This can take a couple resets, but the setup shouldn't take more than a few minutes. Play until the first shop and ensure the following are true:

1. Scroll to the end of the adventure and click on Lissandra. She must NOT have the 'I am Inevitable' power that gives her units stats when surviving damage. That power can often be a guaranteed loss.
2. In one or two rerolls, obtain the 'Counterfeit Copies' power to start. It is a 'pity' power, so have a very high chance to obtain it if you forfeit the adventure without winning a fight.
3. In the shop, click on the 'Item's tab, and spend all your rerolls until you run out of money. You want to get two items on either 'Howling Gale' or 'Divine Whirlwind'. If you didn't get any, quit the adventure and try again.

Counterfeit Copies is amazing because each counterfeit is a 'cost reduced' spell that counts towards Janna's 3* ability. If the counterfeited spell is discounted, it retains the discount when copied. Then, block with anything you have available until you hit 6 mana. With Janna in play, you should easily out-value anything and win.

Ideally, try to go along the top route. Then you can end up at the Ethereal Remitter node to try and get the Natural Magic power which makes all cards cost 2 less. This does a ton to help counter Lissandra's mana tax that gives a 3 mana cost increase to player cards after they have played three cards.

The deck deletion effect of 'Watcher' actually becomes a benefit because when your deck is gone, you can counterfeit and fill your deck with exactly the cards you want to play.

Janna is a decent user of Oath-Gems. She can reliably draw into the discounted champions, and each triggers her effects for discounted cards. However, she costs 4, which makes this build a fair bit slower than typical oath-gems users.