So we've run into this problem a couple of times. Say one player gets an encounter card that advances the active mystery, which results in the active mystery being solved. However, the mystery isn't technically "solved" and a new one isn't drawn until after the mythos phase. The next player, on the same turn, also resolves an encounter that results in advancing the active mystery before the new mystery has been drawn. Are you SOL?

That is at least how I have played it.

Advancing an already solved mystery does nothing.

That is at least how I have played it.

Advancing an already solved mystery does nothing.

This is correct. Mysteries are typically solved at the end of the Mythos phase. Until that point, they are still the "active Mystery". So, advancing them does nothing further once the requirements have been fulfilled.

The only way you can modify the Active Mystery card mid turn is if an effect states "Solve the active mystery"

The only way you can modify the Active Mystery card mid turn (...)

I do believe spoiler tags would be a good idea here.

The only way you can modify the Active Mystery card mid turn is if an effect states "Solve the active mystery"

and that effect is I believe only on a Promise of Power card and one For the Greater Good Task (which you can only turn at the End of the Mythos Phase anyway)

There lots of encounters AND unique assets that allow you to advance the active mystery.

The only way you can modify the Active Mystery card mid turn is if an effect states "Solve the active mystery"

and that effect is I believe only on a Promise of Power card and one For the Greater Good Task (which you can only turn at the End of the Mythos Phase anyway)

There lots of encounters AND unique assets that allow you to advance the active mystery.

He was talking about cards that let you solve the active mystery, not advance it. There are only a couple that actually solve it.