There's two major ways to make you consider skipping chapel. Either make you not want to trash your cards (gardens, fountain, many of the submissions so far add penalties to trashing), or give a trasher that is strong enough that makes you not want chapel (donate, cathedral). I decided to go for the latter:
Chapel is very strong trashing but is weak since it provides no way to simultaneously build your deck. So, this card provides both! It's essentially a one-shot mega-copper trasher + remodeler that hands out debts based on how much of an upgrade/remodel/expansion you are doing. You can get burdened with debt, so you need to have a plan to get out of debt with the cards you gain, which makes it kingdom dependent. Sometimes you can get it instead of chapel, sometimes treasures are the only economy you want and Tithings won't work so well.
Clarifying examples:
- From a hand of 3 coppers, I play 2 and buy and play this card. I trash both coppers in play and the copper in my hand. I would take 2 debt and gain an embargo. Each other player chooses to gain 0, 1, or 2 coppers to hand.
- If my hand is 3 coppers and 3 estates, I could play 3 coppers, trashing them when I buy this, and turn an estate into a duchy. I would take 3 debt and each other player choose to gain 0, 1, 2, or 3 coppers to hand.
- If you have no coppers in play, you trash a card and gain a card costing exactly the same amount. You could turn a chapel into a pearl diver, for $1 by buying this card.
The debt is what makes this only
conditionally better than chapel. If there are good economy 4 and 5 costs that help you repay your debt, you're going to trash early and hard. If there aren't, you won't have as good of a way of handling the debt, and chapel (or even bonfire) might be better. That is why I forbid the treasure gaining. Otherwise 3/4 is always very powerful with turning an estate into a gold second turn and paying off the debt. The other player copper gaining cause is to weaken this a tad bit (so bonfire becomes more competitive with this) and to smoothen out the difference between 3/4 openings and 4/3. (The 3/4 player can pay off all their tithings debt on second turn and still do tithings again while the 4/3 player can't as much. The copper gaining lets both players have a 4/4 opening). This could have been an event, but then I had the annoying "take debt at the end of your turn" to prevent instant pay-off, and I did not like that. So, it became a one-shot night to easily deal with the debt problem.