limited-edition mirror platinum card Amex Unveils a Finish: How To Get One ✨ New card, new look!

Morpeko: Morpeko is a very cheap one single prize attacker for Single Strike decks that have recently gained a lot of popularity because of the rise of Mew VMAX

In total you will receive: 41 Card Dark World Deck

If you control a "Tistina" monster: Banish 1 card from your opponent's GY, face-down

Its not exactly an explicitly Merfolk-centric card, but I guess the +1/+1 counter synergizes with some stuff

You may not be able to literally select which cards are going to the graveyard with each discard spell, but by paying attention to what cards your opponent keeps and what they give up, you can try and time your punches to cut off their decisions and paralyze even the most powerful Constructed decks