: Add 
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, 
for each basic Swamp you control.Cabal Stronghold rewards a mana base with a large number of basic Swamps. It normally taps for one colorless mana, but its other ability costs three mana and a tap to produce black mana equal to your basic Swamp count. That makes it a late-game mana engine for mono-black and heavily basic land configurations rather than an immediate substitute for an ordinary black-producing land.
Expedition Map can find Stronghold when your Swamp count is high enough to use it productively. Large spells such as Torment of Hailfire and Exsanguinate provide clear outlets for the additional black mana. A control deck that expects to make many land drops can use the land slot to improve its finishing turns without dedicating another nonland card to acceleration.
The word basic is the important distinction from Cabal Coffers. Urborg, Tomb of Yawgmoth gives lands the Swamp subtype, but it does not make nonbasic lands basic. Those nonbasic Swamps therefore do not increase Stronghold's output. Choosing too many utility lands can weaken the very engine you are trying to support.
Account for the three mana spent activating it and the fact that Stronghold itself must tap. At low Swamp counts, simply using your lands normally can be as good or better. Include it when your deck can tolerate an early colorless land and reliably reach a high enough basic Swamp count for the activated ability to create a meaningful mana advantage.
