Yesterday there was a game that ended in player victory by curious happenstance.

I started the game with the Call the Ancient One spell. A few turns later I acquired The Eltdown Shards unique item.

The Eltdown Shards allowed me to cast Call the Ancient One without me losing sanity.

I chose to cast the spell with a -13 modifier and a sanity cost of 13. Of course my dice pool got to negative, but the rules say that I can still use a single die. So I did just that. I did not succeed, but after spending a clue token, I did succeed. The Ancient One was awakened and immediately had 13 doom tokens removed from it (going to 0) resulting in instant player victory.

Was there an error in how we played it?

I think you made a mistake. According to the FAQ the maximum number of doom tokens that can be removed with Call the Ancient One is 7 .

Oh I see! Thank you.

Also, beware that it's an Eldritch Horror rule that if you have a dice pool equal to zero or lower, you have 1 die to roll. In Arkham Horror, having zero (or less) dice to roll implies you don't roll anything unless you spend clues to gain dice.

Finally, Eltdown Shards allows you to remove 1 single doom token from the doom track by spending 2 movement points and passing a Lore (-2) check, so in any case you couldn't have used this combo

Julia, OP meant "Crystal of the Elder Things" that absorbs an entire sanity cost of a spell up to three times.

Aside from the maximum of 7 that is not explicitly printed on the card, I justify an additional interpretation:

Since the card says "to avoid paying the sanity cost," I argue that your character has to have enough sanity to spend in the first place, before the cost is canceled. I argue this as semantically different than an effect that "reduces the sanity cost of a spell" because in that case, it is the intrinsic cost that is changing.

The reason I argue this is because this spell has a significant impact on the final battle, and it is exploitable. You only need one success to cast a spell, so a handful of clues may very well get you that success. In the same expansion as the Crystal is a skill card that lets you get one success for free . Having these two together makes it far to easy to damage the AO in final combat. I don't want to throw the spell out of my set, but I do need to find a legal technicality that prevents it from being exploitable, and this is the only idea I have that works.

Unfortunately, to be consistent, this argument must also work for the Mask of Vice , in that you must be able to purchase the item in the first place. Originally I independently argued that this should be how this item works because of how many items you can farm out of the town shops, but on the other hand, this item isn't nearly as crucial to the end of the game as Call Ancient One .

Julia, OP meant "Crystal of the Elder Things" that absorbs an entire sanity cost of a spell up to three times.

Uh, right, thanks Chris