The White Palace

At the beginning of your precombat main phase
each turn, add {w}.
{2}{w}{w}, {t}, Sacrifice The White Palace:
Creatures can't attack you or planeswalkers
you control until your next turn. Activate
only if The White Palace is a land.
When The White Palace is sacrificed, if it's not
an enchantment, return it to the battlefield. It
becomes an enchantment and loses all other types.