Some significant changes have been made to the demo:

Card art has been completely revamped. Some of the cards (particularly their upgraded versions) have also been tweaked to make them more interesting from a gameplay perspective and make choosing which cards to upgrade a more strategic decision.

The previous enemy AI will choose a Champion to attack based on their HP + Armor. That behavior has been changed.
Enemies now have a randomized priority target system that changes every turn. Each Champion will be assigned a priority number at the start of turn and enemies will then prioritize accordingly (from 1-3, so the Champion assigned 1 will be the top-most priority target).
This change to the enemy AI was made to bring the game closer to something like Into The Breach, where you have complete information about the enemies and can plan around them to execute your own strategy.

Another system change is regarding how drawing and discarding card works. The current system allows for a card to cycle into itself (discard happens before draw), which makes an infinite combo way too easy to pull off. The current system will call upon the effects of the played card (including card draw) before discarding said card (similar to how Slay the Spire works). So an infinite cycle with just one card is no longer possible. But you can still achieve something similar if you have 2 or more cards that cycle.

That's all I have. Try out the new demo and let me know what you think!