2009-02-01 : The affected land loses its existing land types and any abilities printed on it. It becomes the chosen basic land type and now has the ability to tap to add one mana of the appropriate color to your mana pool. Grixis Illusionist’s ability doesn’t change the affected land’s name or whether it’s legendary or basic.

2009-02-01 : You choose a basic land type as the ability resolves.