Our RtL campaign is progressing nicely. I opted for Ascension and the Spider Queen. My upgrades include silver beasts, silver eldritch, 1 trap treachery, 1 spawn treachery, Focused, Into My Parlour, and Slaggaroth. The heroes are a couple of turns out from their rumor (Hunting the Wyrm, which gives a hero Ironskin). I can't possibly stop them from succeeding at the rumour, because it doesn't have a failure condition like some of them do, but I can make it as painful as possible. I'll get enough XP and time for a single upgrade, and I've got a few options.
1) Upgrade beasts to Gold. This will do very little in the actual rumor, but Slaggaroth is nearby, and he'll get at least one chance to attack first. I really, really, really don't like beasts (mostly due to spiders being so unwieldy), but they're the best on the overland map and Slaggaroth comes with a slew of them. The heroes are well-equipped, so I don't think a TPK is a possibility. If it were I'd be all over the attack, since it would delay them a few weeks. But I'll probably get some XP and put some poison out.
2) Upgrade eldritch to Gold. This'll beef up the ice wyrms in the rumor quite a lot, along with every eldritch creature in a lieutenant's retinue or dungeon level. It can't stop them from killing the wyrm, but would get me more XP along the way. It would still be somewhat useful in lieutenant encounters, as it would let me pull in Dark Priests and Shades. Shades will be especially nice in lieutenant encounters, as Ghost + Shadowcloak makes them immune to the two melee characters in the party. Soar would normally do that, but the group's wizard gets up to +5 range, so Soar isn't as useful at protecting things from him. Then again, that's 9 treachery to play those, and I'm only getting 3 per turn thanks to a Cautious hero. Couple it with needing 6 to play Dark Charm and I'll never actually play those spawns unless I've gotten event treachery first.
3) Buy a point of event treachery. For dungeons this would become Crushing Blow. For lieutenant encounters (except for Merrick) it would become Danger and a Rage or a Charge. Merrick's free 15 threat would mean it could be a Crushing Blow in his encounters as well. Though for at least a little while it would be useful as a Crushing Blow all the time, since they're still got some nice copper cursed gear I'd love to destroy.
I'm leaning towards 2 or 3 right now, but might not actually have enough XP for upgrading Eldritch. I'm somewhere around 20 right now, with one level left of their dungeon. So I think I've got to kill at least 2 heroes or that's not even an option.
Ok, I'm done thinking out loud. Thanks for listening.