Norn's Annex

({p/w} can be paid with either White or 2 life.)
Creatures can't attack you or planeswalkers you control unless their controller pays {p/w} for each of
those creatures.
No stronghold is impossible to take. The Vault-Cities' defenses are no exception. However, they are designed
to inflic a lot of casualties to Endrek's armies, so the
few survivors can be easily picked off by sentinels.