And here we are.
So I was looking for some excitement; what I meant I suppose was for the Shelters to be potentially useful to the deck, unlike the ones in Dark Ages that only give Necropolis. You often want to trash Estates anyway, so the other 2 aren't that interesting. And there are quite a lot of different possibilities with the Shelter idea, yet at the same time it's very possible to make the game worse. So to see how you did...
Cave/Cabin/Hollow Tree (faust)
Cave: a situational Copper that rarely has an effect on the opening, but is a fun twist when it does work. Going late it's a bit more reliable. Making it an Action would be a bit cleaner, but could be too strong in the opening (and complete Courtier) so is wisely avoided.
Cabin: if you keep the other two cards in your deck this is a Province. Quite a powerful impetus, so if everyone's doing this decks against thin or cycling opponents that have at least one good Treasure are at a slight advantage.
Hollow Tree: puts a Treasure back onto deck, almost never itself. You can get a bit of shuffle control putting Coppers back early, besides other neat little tricks. Something you wouldn't mind coming up often in all random games.
Overall: a good start-off. Encouraging a deck to keep Hollow Tree in it is nice, whilst Cave adds a bit of player interaction. Cave might go better with a shelter that makes shuffles happen more, to get the most out of it.
Ill-gotten Treasury/Dry Moat/Secret Estate (majiponi)
Ill-gotten Treasury: trash for 3 Coppers to hand, now that's going to warp the start quite a bit with the possibility of 5/5, 4/6 or 3/7, though yes with 2 extra cards in the deck first shuffle. A bit like Banquet, so you won't always use it. Quite nice.
Dry Moat: trash to block an Attack, it's quite neat to help stop an opening Attack potentially taking other players out of the game, if it's in hand.
Secret Estate: if you trash it it still gives 1 VP. This gets you no further ahead or behind points wise (everyone's got this), just the card out the deck; so this is weaker than Overgrown Estate.
Overall: Moat and Treasury anti-synergise a bit. The main bit of excitement here in Treasury is not often very fun.
Boneyard/Hole/Dilapidated Estate (Chris is me)
Boneyard: straight 1 Villager, more reliable than Necropolis early and lets you get Villages into the deck later. Not so good late game, it likely saves a spare Action for later.
Hole: if used in the opening, it kinda makes the starter deck just 8 cards and one of your starting hands 3 cards, and you get some choice over the missing other card. Quite a big speed boost, but there are of course cases for using it later or not at all.
Dilapidated Estate: every Shelter gives 2VP if this is in deck. It's a fine choice for a Shelter mechanic. It puts a little question mark on using Hole.
Overall: almost every game is going to be about making an engine, but with a few options about how you use these Shelters to build it. The main question here is how often keeping Hole for VP is worth it, if it actually is an interesting decision.
Cove/Sanctuary/Belfry (hypercube)
Cove: puts 2 cards away for next hand, a handy effect mitigated by no draw or +Action. Drawn turn 1 and any saved Coppers can buy a $5+ that can go into the first shuffle. Drawn turn 2 and 3 cards miss the shuffle and a $3-$5 is put in. So there's a possible unfair advantage for some there.
Sanctuary: a one-off trash that ideally needs a bit of work, sweet. Cove can let this trash 2 more things, making a different boost to drawing it turn 1. You can only add a $2 in though, to balance things a bit.
Belfry: a +Villager Treasure if it's the only Treasure in play. The only reason to keep this is when a treasure-less deck is possible, or you set up dud turns with Cove, otherwise it falls with the Sanctuary.
Overall: I do like the synergy between these three, the different things they can do. Cove can speed up the first shuffle, calms down in impact later. It's just how much of a difference drawing it turn 1 or 2 will make.
Commons/Dowry/Workhouse (Fragasnap)
Commons: one non-Victory gained can be put in hand, this is strong when you can play the gain. On average not much, but occasionally great, power level feels spot on.
Dowry: a one-shot you want to pop late game, now that's a good Shelter premise in my mind. This encourages you to build up to a massive $ mega turn, or it can be more modestly used as an urgent buy during building. A question playtesting would have to answer is how often the mega turn route is dominant; too much so would be bad.
Workhouse: an interesting VP method that involves all the $2-s in the game, with +4 Actions on trash that can help save a turn, maybe the Dowry turn. Like the other varying VP Shelters here, it adds reason to keep them all. You might be moved to keep an uninteresting Commons, doesn't change Dowry but makes up here by including non Shelters.
Overall: each have good design in their own right, and have some synergy. Great, certainly exciting, the only thing is how Dowry might narrow the game a bit.
Pig/Shack/Old Shrine (Gazbag)
Pig: non-terminal buy that you can lose if you don't buy anything. Seems a shame to have to get a Copper in exchange, you lose that buy, but if the first version of Hovel had issues...
Shack: becomes a Lab with Gold in hand, nice way to make a Shelter relevant later.
Old Shrine: a sharp punishment for trashing this, each other player can gain a Gold that can activate their Shack. Doable with handsize attacks of course.
Overall: safe set to replay with, but the only excitement as such is activating Shack. Shrine detracts from this somewhat.
Empty Field/Shack/Stick (Doom_Shark)
Empty Field: changes into a $2, you really want there to be a $2 in the kingdom or possibly cost reduction, otherwise this is a Copper (or the Estate it would have been anyway).
Shack: Estate that you can make a Copper on trash. You'd lose a VP and gain a weak card, I think I prefer Overgrown Estate or an ordinary Estate.
Stick: you trash 2 cards in the opening at no loss of $, this makes things a bit too fast.
Overall: hard to say that I would use these over 3 Estates.
Allotments/Lost Place/Chicken Market (King Leon)
Allotments: cute, tiebreaker and tfb fodder go together fine.
Lost Place: Curses are made relevant to every game, which is nice. The very slow trashing hits the balance spot well, you may want to keep it or not. Softening oppressive early cursing Attacks is great. But you can also change Allotments to a $3 in the opening, speeding things up a bit for those who get them together. The randomness can be unpleasant.
Chicken Market: situational Ruined Market highly dependent on virtual $ or Gold gaining to do anything. It mitigates Lost Place changing Allotments to Silver a little bit. Some 3-card openings possible, but most likely for trashing, even with Lost Place into Copper.
Overall: it's all about Lost Place pretty much, which isn't a bad reason to use the set, just the chance of connecting to Allotments in the opening sets it back.
Savings/Savings/Drought (hhelibebcnofnena)
Savings: 2 Capitals worth $1. Opening splits can vary depending on how they divide between the turns ($7 total for both on turn 1, $8 for 1, $9 for 0), so although there's a bit of flexibility, there's potential for unpleasant random advantages.
Drought: untrashable junk. It stays out of the way if you can (Island it or) use an Action on it just before you shuffle, so the earlier it appears in the shuffle the more Actions you could need to make it work. A mild mitigation to the opening boost of the Savings later on, although it always keeps out of the first shuffle.
Overall: the start becomes heavily affected by chance, turn 3 recovery won't be much to deal with.
Overrun Duchy/Anvil/Allowance (mail-mi)
Overrun Duchy: more often than not a delayed Duchy, when you get it with a Province in hand. There's a bit of skill involved to pop it, but nothing that general good and bad play won't affect. It's alright.
Anvil: delayed Lackeys draw, the needed Action needs to be non-terminal. Cute if you can involve it in an engine.
Allowance: rather like a single Savings. The advantage of drawing it turn 2 is more modest than with the above set, but still a little setback.
Overall: individually each is mediocre, but no two are similar. There’s nice variety, and they could be a pleasant set.
Ore/Helper/Homestead (NoMoreFun)
Ore: becomes a copy of a Treasure you gain. A Silver or maybe Quarry in the opening, or a $5+ later. Nice decision-making called for.
Helper: same as Ore but for Actions. Same pleasant strategizing, and here especially the fact you can't make this a $5 in the opening is an elegant touch.
Homestead: same as Ore but for a Victory. Very often it will be saved for a Province, which can be like taking a whole extra turn so be a big speed boost. The top-deck isn't much of a slowdown considering.
Overall: Ore and Helper are great, Homestead I'm not so keen on. Some random advantages are possible too.
Clergy House/Gingerbread House/Hunting Tent (Tejayes)
Clergy House: trash top of deck, highly risky after turn 1 if not for Hunting Tent. There's a bit of random advantage for those drawing these together.
Gingerbread House: you can try to preserve the 2VP, but the Tent or other Patron triggers will eat it and the clergy or another trasher will get the leftovers Curse. I can see Tent being heavily used at the start, so it's like a more fun, two-stage Hovel.
Hunting Tent: Treasure that scales better going late...or so it seems. Having several Actions on your deck at the Buy phase isn't going to be the best of decks. That's quite funny! Yet as a sorter it's just for Clergy House most of the time because it's in the Buy phase, so suitably weak overall.
Overall: Clergy House and Tent will make deck control easier, but not so much as to warp the game. It's quite fun too.
Chieftain Hut/Copper Vein/Sweeper’s House (Commodore Chuckles)
Chieftain Hut: terminally save 2 Actions to play next turn, an effect that is distinctly useful sometimes but is suitably weak, a good Shelter.
Copper Vein: gain Copper to hand, yes it can make the opening $8 total but gets away with it by one more card in the deck. So it's sound.
Sweeper's House: discard top 2 from deck, situational yet weak like Hut so is again sound.
Overall: no real similarities, so it feels like a set pleasant to play with nice variety. Cute when one of them is useful.
Foodstall/Spire/Clue (MeNowDealWithIt)
Foodstall: non-terminal next-turn-Market Square. You play it whenever it's in hand, maybe the Buy will be useful next turn. You'd only trash it because it doesn't draw. Sort of uninteresting.
Spire: Ruined Village with Fortress effect, purely tfb fodder with its $3 cost and almost useless without any tfb cards in the game.
Clue: can trash when you gain more than 1 card in a turn. It synergizes with Foodstall, and is a nicer Hovel more suited to engine building.
Overall: safe set, but nothing here excites me that much.
If we took the sets apart and then picked 3 to go together, there would be a lot of great combos. I was almost tempted to put my favourite up, but couldn't really choose.
Shortlist: Cave, Cove, Boneyard, Commons, Overrun Duchy, Clergy House, Chieftain Hut.
Winner: Commons/Dowry/Workhouse by Fragasnap.
Runner-up: Chieftain Hut/Copper Vein/Sweeper's House by Commodore Chuckles.
Fragasnap's set of Shelters have convincing reasons to be kept, are quite replayable, don't affect the opening yet also can be justifiably trashed. Commodore's set is likely going to be safer in playtesting, but I just wasn't so excited by Copper Vein.
There are definitely good reasons to choose other sets here, or a combo from different sets, so I can see this contest coming up again in future. Congrats and well done all!