edhseer Commander synergy, explained
Land
As this land enters, choose a creature type.
Add {C}.
activated {T} — adds 1 mana
Add one mana of any color. Spend this mana only to cast a creature spell of the chosen type, and that spell can't be countered.
activated {T} — adds 1 mana
Causes: nothing.
Cares about: nothing.
a land enters the battlefield — 1,560 cards in the game can cause this (Cavern of Souls is one).
When Cavern of Souls enters:
199 other cards care about it too. These are the ones with the most connections.