The good old A Test of Will reads: "Cancel the 'when revealed' effects of a card that was just revealed from the encounter deck." The 'revealed from the encounter deck' part has me wondering. When a Witch of Angmar ("When you resolve shadow cards dealt to Witch of Angmar, if they have the Sorcery trait, resolve their "when revealed" effects. (Resolve any shadow effects first.)") is dealt a Sorcery treachery as a shadow card, can you cancel the 'when revealed' effect with A Test of Will ? I mean, in that weird case, it wasn't really revealed by the encounter deck but you still have to resolve its 'when revealed' effect.

I have always played that you cannot cancel such effects with A Test of Will.

Telling you to resolve its when revealed effect is different than saying reveal it.

Didn't we have a ruling that said Thalin cannot damage enemies who are coming out of the discard pile (because it's not "the encounter deck") , or from a secondary deck such as the Raven deck in The Antlered Crown? That logic would apply here as well, so because the treachery was not revealed from the encounter deck, you couldn't use A Test of Will on it.

There is a very long thread about the topic.

The meat of it was this response from Caleb:

Hi Richard,

Thanks for following up with me.
My ruling with regard to Thalin was based on the use of the language “by the encounter deck” as opposed to the more prevalent phrase “from the encounter deck.” A strict reading of the core rules makes it seem encounter deck only reveals 1 card per player during the staging step. However, after reviewing other player card effects that use the language “by” and “from” the encounter deck, it seems clear to me that both words were used to mean the same thing from the beginning of the game.
Therefore, I am changing my answer to the question that sparked the debate to say that Thalin ’s ability will trigger against each enemy revealed “by” or “from” the encounter deck while he is committed to the quest. This includes enemies that are revealed by a surge effect or through card effects that instruct you to search “the encounter deck and discard pile” for that enemy. Essentially, the phrases “by the encounter deck” and “from the encounter deck” should be taken to mean any card that originated from the encounter deck or discard pile.
Some exceptions to this rule would be:
- Enemies that were previously set aside and revealed during the quest phase
- Enemies that are revealed from some other deck (i.e. the Underworld deck in The Steward’s Fear)
I will make a note to add this rules clarification to the next FAQ.
Cheers,
Caleb

Although this question is slightly outside the scope of Caleb's response. The shadow card did originate from the encounter deck...

But I still think Test of Will is invalid. You are not revealing the card, you are resolving the when revealed effects.