edhseer Commander synergy, explained
Land — Gate
This land enters tapped.
As this land enters, choose a color other than blue.
Add {U} or one mana of the chosen color.
activated {T} — adds 1 mana
Causes: nothing.
Cares about: nothing.
a Gate enters the battlefield — 25 cards in the game can cause this (Sea Gate is one).
When Sea Gate enters:
a land enters the battlefield — 1,560 cards in the game can cause this (Sea Gate is one).
When Sea Gate enters:
200 other cards care about it too. These are the ones with the most connections.