Lands you control and land cards in your library are basic.
(14/10/2022)
Lands that become basic are no longer nonbasic lands. This may change what effects can apply to them. For example, if an opponent controls Blood Moon, an enchantment which says “Nonbasic lands are Mountains,” and you play Rootpath Purifier, Blood Moon can no longer apply to the lands you control because they are all basic.
(14/10/2022)
Being basic doesn’t grant any abilities to a land that it didn’t already have, and doesn’t remove any card types, subtypes, or supertypes. For example, a land card that is legendary will be both basic and legendary while on the battlefield or in your library.
(14/10/2022)
Notably, becoming basic also doesn’t grant any of the basic land types. If an effect instructs you to search your library for a basic land while you control Rootpath Purifier, you may search for any land card in your library. However, if an effect instructs you to search your library for a card with a basic land type, you must search for a land that is a Plains, Island, Swamp, Mountain, or Forest, regardless of whether or not the land is basic.
