Most of the time, you'll cascade into another permanent thanks to the decklist's low non-permanent spell count
Mill as a win condition in Commander is a big ask since decks have 99 cards, but Hope combined with all the lifegain support makes it much easier to realistically accomplish the mill goal
Because of this, Mermails variance based style allowed it to accept the losses to macro / difi, and focus on the six or so faces of very high value rolls which were enough to reach the winning threshold over fire fist without progressing to the late game, or at least reach the late game with correct set-up (waters for Tidal in grave, and preferably a controller in hand)
Distributed exclusively to WPN Premium stores in tiny quantities, they are highly sought after due to their extreme scarcity, though this one is worth just a whisker more than #8 on this list
Fusion Monsters are in the Extra Deck, so they did not need to be searched