Shuffle your hand back into your deck and draw a new 7 card hand
In real games, that trade is almost always worth it
If control or midrange decks can't deal with your indestructible creatures, that's a great way to close out the game, even after your opponent has stabilized
The most common case is that you just dont play the game anymore and have no real intentions of coming back to it
That said, The Dark included exactly one land that produces mana: City of Shadows
Not background necessarily, but some other line of text that says something along the lines of Whenever you sacrifice a Treasure token, give a creature a +1/+1 counter and trample until end of turn. That would make it a lot more interesting and powerful, but I suppose not every card needs to be great