Here's something that came up not so long ago. At the time, I just made a quick decision and carried on, but I wanted to ask for everyone's opinion: when battling an Ancient One whose attack becomes more potent each round (Yig, Hastur, Ithaqua, Shub-Niggurath, Yog-Sothoth, Nyarlathotep, Ghatonothoa, Y'Golonac), does the increase in power still occur in rounds where the Ancient One does not attack (because the attack is canceled by an item or Ally, or because of an Epic Battle card)? That is to say, if I were battling Ghatonothoa and canceled his first attack, would I have to spend one or two movement points the second round?

I don't remember the exact wording of the non-base AOs, but if it says the attack gets more difficult every round (the word "round" is your indicator), then attack cancelers do no t halt the progression of the AO's attack (since the rounds have still passed). I believe this answer is freely available somewhere.

Effects that are listed as part of the attack, such as Cthulhu's doom healing, are canceled, since it is the activation of his attack that triggers it.

Curses. So Ghatonothoa would have annihilated us even more thoroughly than he already did. Or wait...I suppose we could have just canceled his attack on the round he would have annihilated someone. Although...still worse off for us, because only one person would have lasted an additional round, since we all had separate speeds. Thanks, Tibs.