I just lost a game because my two Phoenix and one red dragon randomly decided not to attack, despite their being NOTHING in play that would prevent it. The Elder had Morning Star, some pillars, and a Sundial up, and that was it. My field was my above-mentioned creatures, some pillars/pendulums, and Fire Shield.
I used the two Firebolts in my hand to bring the Elder within my creatures' killing range - I was poisoned and had 2 or so HP left, so this was my last chance. By all accounts, I should have won, as my creatures' total damage exceeded his remaining HP.
Except, as if they were secretly double-agents, my creatures didn't attack once I ended my turn. The poison then killed me. This has happened twice so far, but this time was the one that irritates me, since I was actually going to win.
