As this artifact enters, look at an opponent's hand, then choose any card name. Activated abilities of sources with the chosen name can't be activated unless they're mana abilities.
Castle Garenbrig enters tapped unless you control a Forest. {T}: Add {G}. {2}{G}{G}, {T}: Add six {G}. Spend this mana only to cast creature spells or activate abilities of creatures.
Without Garenbrig's strength, the realm would succumb to the wilds.
Castle Locthwain enters tapped unless you control a Swamp. {T}: Add {B}. {1}{B}{B}, {T}: Draw a card, then you lose life equal to the number of cards in your hand.
Without Locthwain's persistence, the realm would stagnate and die.