Ocean Hag
Action - Duration - Attack
$5
Each other player gains a Curse. At the start of your next turn, you may trash a non-Victory card from your hand, for +1 Card.
Donald X has commented that there are two reasons that if he ever updates Seaside, he’d likely replace Sea Hag with a different cursing attack. First, players don’t like attacks that don’t provide any benefit. Second, Seaside has two <$5 cards that can junk your opponent (Ambassador), which is too many, and Ambassador is more unique.
Here I’ve envisioned its replacement. The Ocean Hag happens to be a perfect counter to a Sea Hag because it can trash curses from Sea Hag right away, even though this wouldn't matter much in practice as someone probably wouldn't own both. Like Ambassador, it can give junk to your opponent while getting rid of yours. But, unlike Ambassador, the fact that it’s a $5 duration and gives junk that runs out (Curses) should keep it from being too powerful.
Dominion doesn't have trashers limited to non-Victory cards. That's probably because, unless a junker is present, the most commonly trashed cards are Treasures and Victory cards, so saying Treasure is simpler. Because Ocean Hag is a junker, it's a great candidate to be limited to non-Victory cards. This also should keep the power level of the card in check, relative to the original.
Original version:
Ocean Hag
Action - Duration - Attack
$5
Each other player gains a Curse. At the start of your next turn, you may trash a card from your hand, for +1 Card.