Commander 2014 brought us
Impact Resonance, a card which functionality seems all but clear.
Gatherer gives us some basics, but fails to describe a common scenario.
Let me illustrate the problem with an example:
Ruric Thar, the Unbowed is in play. I play two spells (say,
brainstorm and
ponder), which results in Ruric dealing me a total of 12 damage. I then play
Impact Resonance. From Gatherer (see link above) we know that Rurics trigger from playing Impact will not be included in the amount of damage to be dealt. But there is an ambiguity regarding how to interpret how much damage Impact will deal.
Reasoning A:
“Greatest amont” is interpreted as of each effect. This perspective, which is widely suggested on web forums, indicates that in the example above Impact will yield 6 damage. And
Pestilence would only yield 1 damage no matter how many activations you do.
Reasoning B:
“Greatest amont” is on source/receiver basis. I.e. accumulated. So for each pair of source/receiver, find the maximum amount of damage dealt. In the example above, Impact would yield 12 damage to distribute. And
Pestilence would yield X damage, where X is how many activations you do.
I would expect a clarification of e.g. "…the greatest amount of damage dealt by a source to a permanent or player
at a single moment this turn" if version A was intended. But I can see the possibility of either being the intended functionality.
I believe an official answer is needed on this one, as speculations seems to be widespread whilst I have failed to find any official ruling. My guess is on version B, mainly based on the lack of clarification as described above, and based on rulings regaring
Ogre Enforcer