Solution 1: The Bane card is Scheme. You play it every turn and use it to set itself on top of your deck.
Solution 2: You play KC/Scheme and the Bane card, choosing to set all three on top of your deck at the end of your turn.
Solution 3: You play Haven and set aside the Bane card.
Solution 4: You discard the Bane card during your turn, then use Inn/Herald/Scavenger to put it on top of your deck for next turn.
Solution 5: You play Courtyard/Mandarin/Count each turn, placing the Bane on top of your deck.
Yeah, I just kind of threw these out there without checking if they work. I looked at them again in the case the rest of my deck is a shuffled pile of Ruins, Curses, and whatever else I want/need to have.
1 works because it's Scheme. But then the Bane card has to be Scheme, so it doesn't work with any other Bane. I guess the rest of these need other cards in the Supply though, so I suppose there's nothing wrong with specifying the Bane card.
I'm pretty sure 2 works, since it doesn't depend on the rest of your deck. Probably the best solution for any Bane other than Scheme.
3 doesn't work, cause as eHalcyon pointed out, it has to be in your hand every turn, not just your own.
4 depends on the contents of your deck, so they don't work without more combo behind them to get all the cards you need on top of your deck every turn.
I think KC/KC/Scav/Scav/Discard/Bane works every turn, with 2 more KC's, 2 more Scav's, and another copy of the discarding action in your deck. Also, since that's 6 cards, you have to either use something that draws and discards(Hamlet, Oasis, etc.) or something that discards the top card of your deck(JoaT).
Herald and Inn work as long as you can keep buying them, but eventually you'll run out of them. You just have to be able to ensure the game ends before then, I guess.
Since the cards have to come from your hand for 5, I don't think any of them can work every turn; you'll draw up whatever you put on top last time, minus the card you used to put them on top, plus Ruins/Curses.