Damn, that last battle was seriously sweaty. Those big nasties that grow stronger whenever you do anything almost got me. Then I got lucky with a frogger from the portal, took one of the bastards out, and then managed to grind my way into turning the tide. Won with 1 hp left, and no more cards to draw.
Improvement suggestions:
1. If the text log was less verbose (ie fit on a single line) it would be easier to follow what happens. 2. Totally-not-an-ambull threw a dude so hard his hit-box broke. Couldn't click him to make him move. Buggy indeed. 3. At times I felt like the arena was too large. But then again, with that final battle being such a nail biter, maybe you have it just right.
Well done dev!