I'm not sure if my game group resolved our initial mythos card right. Our choice was get rid of the ally deck or resolve midnight effects again. We chose the latter so it triggered one of our encounter cards to " curse all investigators". This gimped us quite a bit and we lost fairly quickly. The base game manual says midnight effects are not triggered on the first turn. Did we play it right?

Midnight effects are never triggered during setup. Hence, having a dual chance, you were forced to choose the one that was resolvable, i.e. returning the Ally deck to the box.

I don't remember if in UF there was a clarification about this, but this is a standard rule in many FFG games and a rule that appears also in Gates of Arkham (regarding the split rewards / penalties), so, I'd rule this way. Thematic-wise, look at the thing under this point of view: cards offering you a choice always come with particularly nasty effects, so that you actually have to choose the "lesser of two evils"; if one of the effects is not resolvable due to rules, then you should automatically choose the other

(in any case, I'd be curious to hear the rationale behind your choice: you don't need Allies to win, and rarely they are given as rewards, while on the other hands an "everyone's cursed" with zero trophies to clear the curse appear to be incredibly tough on investigators)

What Julia said, Allies, pfft, toss 'em. Maybe final combat against Glaaki becomes unwinnable, but then again, point (for me) is to win before AO wakes up. I also tend to choose the close Entrance(s) option over doom token adding options.

I also tend to choose the close Entrance(s) option over doom token adding options.

Same here. I never use the Entrance options (make the game too easy) so that closing them is really not a problem

We were indeed battling Glaaki. In hindsight though...sacrificing the ally deck would have been way less painful because we botched our first 11 encounters and were hanging by a thread until the end battle was triggered.