Dominion already has an astonishing number of different kingdoms, but some cards compound that variety even further.
Your challenge is to design a card or landscape with setup rules that make it functionally a lot of different cards.
The clearest examples from the official cards are Druid, Riverboat and Way of the Mouse. Obelisk and Traits can potentially add a lot of variety too if it makes you rethink the card it applies to (E.g. Reckless). Same with Liaisons, and some Liaisons are more impacted by what the Ally is than others
No firm rules about what's in or out (E.g. not sure whether Ferryman or Band of Misfits "count", though they aren't what I had in mind). But I am looking for card (shaped things) that are different each game, so something like Pawn wouldn't count even though it's a bunch of cards at once. Online I should want to check and care about what the card (shaped thing) does in this game.
Looking for relatively simple ideas that create interesting cards. Balance can be hard with such variety (e.g. Riverboat can vary a lot) but it's worth trying.
Split piles etc. are fine.
Edit: For clarity, I really like Riverboat and Druid, and that's why I picked this prompt