Destroying the source of an effect

This has been a topic of considerable debate with the people I play with, and I'd prefer to hear an official ruling.  That said, I'll include what I've been going by in the mean time.

My unnofficial ruling has been to have hinged on the actually spacing on the cards.  I consider single paragraphs a single effect.  All reactionary effects trigger immediately, but the effect keeps going until the paragraph is done.  After everything is resolved from that paragraph, the next one takes effect if the source is still in play.

If lava is spewing from a volcano and everything will be damaged, I expect it to hit everything even if an effect stops the volcano.  The lava is already on the way, the way I see it.  I found stopping things like this in the middle almost always made the game too easy because the players could manipulate things too much.

Effects in separate paragraphs I consider to be a separate phase of the card.  If you're playing a card to deal damage and gain health, but the gaining is in the second paragraph, I would say that the hero could go down from a revenge attack before gaining the health.  However, cards that target multiple targets one step at a time, like Chain Lightning, do not just end if the first one dies, but would end early if Tempest went down.  Revenge that would only occur during damage delt by the 3rd paragraph of Chain Lightning would not occur until the damage in paragraph took place, so Tempest could survive through the last hit if the player chose the target order carefully.

I don't have the cards with me ATM so I was winging it on the references.

I'm with Agent Bon on this except that I tend to interpret sentences, rather than paragraphs, as a single effect.

Early on in the forums (not sure the exact link) I created a hypothetical situation where a card dealt damage to all heroes.  The it had previously been stated that in a situation like that, the heroes determine order.  In my hypothetical, I had the card deal damage to Ra.  I then had Ra immediately deal damage back to the original target.  That destroyed the target, thus cancelling the damage to be dealt to the other heroes.  Someone (I believe Paul) said that this is correct.  Basically, the moment a card is destroyed, any outstanding effects of that card (or at least any outstanding damage to be dealt by that card) are cancelled.

This is answered in the official errata pinned at the top of the forum.  Look under Other -> Ties, timing, etc.  They have a specific example about a card dealing damage to all heroes and Ra's Flame Shield.

OK, Jeff, I now agree with your assessment of Wrest The Mind. If the wrested target dies taking 3 psychic damage from Visionary, that causes Wrest the Mind itself to be destroyed and Visionary doesn't have to take the 3 psychic damage to herself.