Finally, if you want to build a dedicated theft deck in Dimir, then Dragonlord Silumgar is for you
That means that not only can a fetch land find actual Basic Lands, but it can also find non-basic lands that happen to have those Basic Land subtypes
This is one of the best and most extreme implementations of sneak, but it takes the card from being a possible inclusion to a must-have for milling decks, and maybe even at three or four copies, too (in Standard)
The ability to exchange one resource for another gives players plenty of choice on how best to use their creatures, lands, and spells to find winning combinations (more info on the theory behind that here)
This is a little bit clunky and you have to be careful about when you cast it -- but when the coast is clear, it's going to kill something and make your creature a better attacker at the same time