Activate only as a sorcery." A few creatures explore because of an activated or triggered ability that doesn't target the creature
When you're dumping your land-filled hands onto the battlefield in a hurry with cards like Summer Bloom and Manabond, you'll quickly run out of cards
You need the City's Blessing, and for the creature to stick around on your board dodging removal for a whole turn before you use its ability, and after you do so, the Navigator jumps to the bottom of your library, never to be seen again
Ive played cards like Haunted Fengraf in the past for this very reason, and Eden, Seat of the Sanctum looks so much better
Then listen to the sweet sound of your opponents telling you how much they hate you
Some involve an imbalanced resource conversion, like [casthaven]Ancient Tomb[/casthaven] (two life is absolutely worth an extra mana), others rely on a resource strong enough to easily build a deck around, such as [casthaven]Tolarian Academy[/casthaven] and [casthaven]Mishras Workshop[/casthaven]