Ok, let me fix a couple. Let me know what you think. First, let's make Mummy play by the rules better:
Mummy (2.0)
Duration
Cost: 4
You may trash a treasure from your hand. If you do, you may trash a Curse from your hand.
While this card is in play, any other player who gains a treasure also gains a Curse. Each time this card is in play, it can cause each player to gain at most one Curse.
At the start of your next turn, turn this card upside-down.(*)
(* - As previously discussed, this is simply so the Seaside rules know how long Mummy stay in play; there could be cards that stay out even longer, but Donald didn't release any.)
---------------------------------------------------------------
Ok, let's make Werewolf a little more fair maybe? Now the mechanism involved is somewhat swingy, but probably fair. I'm not sure.
Werewolf (2.0)
Cost: 5
Action-Attack-Duration
+1 card
+1 action
At the beginning of your next turn, each other player reveals cards from the top of their deck until revealing a card costing between 3 and 6, setting it aside and discarding the other revealed cards. If the set aside card is a Silver, the player draws it and then discards a card in hand. If the set aside card is not a Silver, the player chooses to either trash that card or discard it and gain a Curse.
When you gain this card, gain a Curse.
Remark: After the Curses run out, it's still a reasonable Cantrip delayed attack that forces players to discard a good card every time they don't reveal a Silver. You probably won't buy a ton of these anyway because of the on-gain.