Basically every multicolored legacy deck runs 5-8 fetchlands, some even more. Almost no one runs that many dual lands though; even the greediest decks rarely ha

Basically every multicolored legacy deck runs 5-8 fetchlands, some even more. Almost no one runs that many dual lands though; even the greediest decks rarely have 4 of any single land, but every B/U deck is going to have 4 Polluted Delta to get their basics. Additionally, Delta can be played as a 9th fetch in a B/G or U/W deck too, because it still gets islands and duals, but you wont see an Underground Sea in that list.