edhseer Commander synergy, explained
Land
This land enters tapped unless you control a Mountain.
Add {R}.
activated {T} — adds 1 mana
Creatures you control get +1/+0 until end of turn.
activated {1}{R}{R}, {T} — gives +1/+0
Causes: nothing.
Cares about: nothing.
a land enters the battlefield — 1,560 cards in the game can cause this (Castle Embereth is one).
When Castle Embereth enters:
199 other cards care about it too. These are the ones with the most connections.