Nonbasic lands are Mountains.
122 A25 • ENFranz Vohwinkel — watermark: The Dark
™ & © 1993— Wizards of the Coast
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12/1/2004 Blood Moon's effect doesn't affect supertypes and won't turn any land into a basic land. 6/7/2013 Nonbasic lands will lose any other land types and abilities they had. They will become Mountains and gain the ability ": Add to your mana pool." 6/7/2013 If a nonbasic land has an ability that causes it to enter the battlefield tapped, that ability will still function. For example, if Blood Crypt is entering the battlefield, its controller may pay 2 life to have it enter untapped. Regardless of this choice, it will be only a Mountain and not a Swamp.