The final agenda card in the core set is . . . confusing. This is doubly so for players who want to have a blind playthrough of the campaign. Having just completed the Midnight Masks with its fantastic reveal, why would anyone want to spoil the finale? That's a problem because this card is easy to misread:

Forced - When this agenda advances:

• If the investigators are at Act 1, put the set-aside Ritual Site into play and spawn the set-aside Umôrdhoth there.
• If the investigators are at Act 2 or 3, discard all enemies at the Ritual Site and spawn the set-aside Umôrdhoth there.

The key to understanding the flow of the finale is understanding that "When this agenda advances" means the forced action happens after the 5 doom threshold is reached and not when this agenda card is revealed. For people who read this correctly the flow is sensible:

1. Agenda 3a is revealed giving investigators 5 doom to either stop the ritual (R1) or prepare for Umôrdhoth's arrival.
2. After 5 doom, make sure the Ritual SIte is in play and only has one enemy: Umôrdhoth.
3. The Devourer Below replaces both the Act and the Agenda. It's no longer possible to stop the ritual, but the investigators can defeat Umôrdhoth by either by giving it 6 + 4 per investigator damage (R2) or sacrificing Lita (R3). There's no time limit, but Umôrdhoth is massive (engaged with all investigators if not exhausted) and dishes out 3 damage and 3 horror so the fight will be pretty quick.

So what happens if you misread the card?

1. As soon as Agenda 3a is revealed, the Ritual SIte comes into play with Umôrdhoth.
2. If the investigators are somehow able to stop the ritual with a massive enemy taking attacks of opportunity, they can still get R1. This is unlikely unless they have made significant progress before Agenda 3a has been turned.
3. If the investigators sacrifice Lita, they can get R3 instead.
4. If they somehow survive 5 doom, The Devourer Below replaces the act and agenda. If Umôrdhoth has been defeated they get R2 but are defeated if Umôrdhoth is still alive when the card flips.

Of course this makes an already difficult scenario even harder. If you read it right the first time, you might wonder why anyone would think the game would be so aggressively mean. One reason might be that The Ritual Begins adds unmotivated obstacles:

• enemies are stronger after the previous agenda spawned a monster with doom on it and
• a very difficult will test that will put a madness from the player's collection into their hand.

A 5 doom timer to kill the big baddie seems like more of the same.

The solution, of course, would be to put the Forced action on the back so that it's only revealed when the agenda actually advances. That would fit with how the rest of the core scenario agendas work. My guess is that this wasn't done because the artwork on The Devourer Below side is so awesome.

At any rate, now that I know how this scenario is supposed to end, I'm going to try it again. Up til now I've just ignored the entire finale as unfun and unfair.