By playing a Merlin card and sending it back to your hand with a Mim, you can get twice or even four times the value from their abilities
The cards mechanics reflect that in nuanced ways
Part of your World and Hades Lord of the Underworld allow you to return characters from your discard pile to your hand
Since your opponents have to discard a ton, there's a reanimation sub-theme in the deck
There are several cards in this ink that synergize with items by reducing their costs, returning them from your discard pile to your hand, drawing cards, and more
This "enters or attacks" trigger is insane, because provided you have at least one nonland permanent in your graveyard, Sin is always going to bring it back, and by the time you play him in these colors it's virtually impossible that you don't have stuff to get back