Cards that support Merfolk Tribal seem a great choice for our build
Dimir Charm Twitchy and intricate, Dimir Charm mostly matters for the topdeck manipulation with some bonus interaction in EDH decks like Xanathar, Guild Kingpin or ninjas
With such a low activation cost and no limits to how many times you can activate, Tortured Existence allows you to go infinite in a number of ways, perhaps the spiciest being with poison counters and Syr Konrad, the Grim: 13
Secondly, when a permanent with counters on it is destroyed, Yuna puts an equal amount of +1/+1 counters onto a creature
I have tried a lot to do an all encomapssing one, seems sensible, makes it most playable in limited setting given usually a synergy card
Creature - Vampire Glass-Cast Heart Whenever one or more Vampires you control attack, create a Blood token