Found a bug which was quie annoying.
After summoning ChronoEngine, the second go it would not allow you to skip turn if you couldn't choose a card. It allows you to view to cards, but you cannot do anything other than refresh the page. :(
The last boss is easy w/o any green giants. Just wear down the army before you go in, use 20 brown swordsmen and a defense strategy as soon as you engage.
Probably someone else had the same name earlier :)