edhseer Commander synergy, explained
Land
This land enters tapped unless you control a Forest.
Add {G}.
activated {T} — adds 1 mana
Add six {G}. Spend this mana only to cast creature spells or activate abilities of creatures.
activated {2}{G}{G}, {T} — adds 6 mana
Causes: nothing.
Cares about: nothing.
a land enters the battlefield — 1,560 cards in the game can cause this (Castle Garenbrig is one).
When Castle Garenbrig enters:
199 other cards care about it too. These are the ones with the most connections.